diff --git a/resources/celerity/map.php b/resources/celerity/map.php
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -13,7 +13,7 @@
     'core.pkg.js' => '68f29322',
     'dark-console.pkg.js' => '187792c2',
     'differential.pkg.css' => 'ffb69e3d',
-    'differential.pkg.js' => '59453886',
+    'differential.pkg.js' => '8deec4cd',
     'diffusion.pkg.css' => '42c75c37',
     'diffusion.pkg.js' => '78c9885d',
     'maniphest.pkg.css' => '35995d6d',
@@ -385,8 +385,8 @@
     'rsrc/js/application/dashboard/behavior-dashboard-tab-panel.js' => '0116d3e8',
     'rsrc/js/application/diff/DiffChangeset.js' => 'd7d3ba75',
     'rsrc/js/application/diff/DiffChangesetList.js' => 'cc2c5de5',
-    'rsrc/js/application/diff/DiffInline.js' => '26664c24',
-    'rsrc/js/application/diff/DiffInlineContentState.js' => '68e6339d',
+    'rsrc/js/application/diff/DiffInline.js' => '9c775532',
+    'rsrc/js/application/diff/DiffInlineContentState.js' => 'aa51efb4',
     'rsrc/js/application/diff/DiffPathView.js' => '8207abf9',
     'rsrc/js/application/diff/DiffTreeView.js' => '5d83623b',
     'rsrc/js/application/differential/behavior-diff-radios.js' => '925fe8cd',
@@ -788,8 +788,8 @@
     'phabricator-dashboard-css' => '5a205b9d',
     'phabricator-diff-changeset' => 'd7d3ba75',
     'phabricator-diff-changeset-list' => 'cc2c5de5',
-    'phabricator-diff-inline' => '26664c24',
-    'phabricator-diff-inline-content-state' => '68e6339d',
+    'phabricator-diff-inline' => '9c775532',
+    'phabricator-diff-inline-content-state' => 'aa51efb4',
     'phabricator-diff-path-view' => '8207abf9',
     'phabricator-diff-tree-view' => '5d83623b',
     'phabricator-drag-and-drop-file-upload' => '4370900d',
@@ -1162,10 +1162,6 @@
       'javelin-json',
       'phabricator-prefab',
     ),
-    '26664c24' => array(
-      'javelin-dom',
-      'phabricator-diff-inline-content-state',
-    ),
     '289bf236' => array(
       'javelin-install',
       'javelin-util',
@@ -1549,9 +1545,6 @@
       'javelin-install',
       'javelin-dom',
     ),
-    '68e6339d' => array(
-      'javelin-dom',
-    ),
     '6a1583a8' => array(
       'javelin-behavior',
       'javelin-history',
@@ -1823,6 +1816,10 @@
       'javelin-dom',
       'javelin-workflow',
     ),
+    '9c775532' => array(
+      'javelin-dom',
+      'phabricator-diff-inline-content-state',
+    ),
     '9cec214e' => array(
       'javelin-behavior',
       'javelin-stratcom',
@@ -1913,6 +1910,9 @@
       'javelin-typeahead-ondemand-source',
       'javelin-dom',
     ),
+    'aa51efb4' => array(
+      'javelin-dom',
+    ),
     'aa6d2308' => array(
       'javelin-behavior',
       'javelin-dom',
diff --git a/src/infrastructure/diff/PhabricatorInlineCommentController.php b/src/infrastructure/diff/PhabricatorInlineCommentController.php
--- a/src/infrastructure/diff/PhabricatorInlineCommentController.php
+++ b/src/infrastructure/diff/PhabricatorInlineCommentController.php
@@ -172,7 +172,9 @@
         $inline = $this->loadCommentByIDForEdit($this->getCommentID());
 
         if ($is_delete) {
-          $inline->setIsDeleted(1);
+          $inline
+            ->setIsEditing(false)
+            ->setIsDeleted(1);
         } else {
           $inline->setIsDeleted(0);
         }
diff --git a/webroot/rsrc/js/application/diff/DiffInline.js b/webroot/rsrc/js/application/diff/DiffInline.js
--- a/webroot/rsrc/js/application/diff/DiffInline.js
+++ b/webroot/rsrc/js/application/diff/DiffInline.js
@@ -44,7 +44,6 @@
     _undoRow: null,
     _undoType: null,
     _undoState: null,
-    _preventUndo: false,
 
     _draftRequest: null,
     _skipFocus: false,
@@ -161,14 +160,6 @@
       return this._endOffset;
     },
 
-    _setPreventUndo: function(prevent_undo) {
-      this._preventUndo = prevent_undo;
-    },
-
-    _getPreventUndo: function() {
-      return this._preventUndo;
-    },
-
     setIsSelected: function(is_selected) {
       this._isSelected = is_selected;
 
@@ -452,21 +443,12 @@
         this._undoText = null;
       }
 
-      var uri = this._getInlineURI();
-      var handler = JX.bind(this, this._oneditresponse);
-
-      var data = this._newRequestData('edit', content_state);
-
-      this.setLoading(true);
-
-      new JX.Request(uri, handler)
-        .setData(data)
-        .send();
+      this._applyEdit(content_state);
     },
 
     delete: function(is_ref) {
       var uri = this._getInlineURI();
-      var handler = JX.bind(this, this._ondeleteresponse);
+      var handler = JX.bind(this, this._ondeleteresponse, false);
 
       // NOTE: This may be a direct delete (the user clicked on the inline
       // itself) or a "refdelete" (the user clicked somewhere else, like the
@@ -586,7 +568,6 @@
       this._readInlineState(response.inline);
       this._drawEditRows(rows);
 
-      this.setLoading(false);
       this.setInvisible(true);
     },
 
@@ -617,24 +598,24 @@
       return new JX.DiffInlineContentState().readWireFormat(map);
     },
 
-    _ondeleteresponse: function() {
-      // If there's an existing "unedit" undo element, remove it.
-      if (this._undoRow) {
-        JX.DOM.remove(this._undoRow);
-        this._undoRow = null;
-      }
+    _ondeleteresponse: function(prevent_undo) {
+      if (!prevent_undo) {
+        // If there's an existing "unedit" undo element, remove it.
+        if (this._undoRow) {
+          JX.DOM.remove(this._undoRow);
+          this._undoRow = null;
+        }
 
-      // If there's an existing editor, remove it. This happens when you
-      // delete a comment from the comment preview area. In this case, we
-      // read and preserve the text so "Undo" restores it.
-      var state = null;
-      if (this._editRow) {
-        state = this._getActiveContentState().getWireFormat();
-        JX.DOM.remove(this._editRow);
-        this._editRow = null;
-      }
+        // If there's an existing editor, remove it. This happens when you
+        // delete a comment from the comment preview area. In this case, we
+        // read and preserve the text so "Undo" restores it.
+        var state = null;
+        if (this._editRow) {
+          state = this._getActiveContentState().getWireFormat();
+          JX.DOM.remove(this._editRow);
+          this._editRow = null;
+        }
 
-      if (!this._getPreventUndo()) {
         this._drawUndeleteRows(state);
       }
 
@@ -693,7 +674,6 @@
       var anchor = cursor || this._row;
       cursor = cursor || this._row.nextSibling;
 
-
       var result_row;
       var next_row;
       while (row) {
@@ -837,8 +817,10 @@
 
     save: function() {
       if (this._shouldDeleteOnSave()) {
-        this._setPreventUndo(true);
-        this._applyDelete();
+        JX.DOM.remove(this._editRow);
+        this._editRow = null;
+
+        this._applyDelete(true);
         return;
       }
 
@@ -846,35 +828,56 @@
     },
 
     _shouldDeleteOnSave: function() {
-      var state = this._getActiveContentState();
+      var active = this._getActiveContentState();
+      var initial = this._getInitialContentState();
 
-      // TODO: This is greatly simplified because we don't track all the
-      // state we need yet.
+      // When a user clicks "Save", it counts as a "delete" if the content
+      // of the comment is functionally empty.
 
-      return !state.getText().length;
-    },
-
-    _shouldDeleteOnCancel: function() {
-      var state = this._getActiveContentState();
+      // This isn't a delete if there's any text. Even if the text is a
+      // quote (so the state is the same as the initial state), we preserve
+      // it when the user clicks "Save".
+      if (!active.isTextEmpty()) {
+        return false;
+      }
 
-      // TODO: This is greatly simplified, too.
+      // This isn't a delete if there's a suggestion and that suggestion is
+      // different from the initial state. (This means that an inline which
+      // purely suggests a block of code should be deleted is non-empty.)
+      if (active.getHasSuggestion()) {
+        if (!active.isSuggestionSimilar(initial)) {
+          return false;
+        }
+      }
 
-      return !state.getText().length;
+      // Otherwise, this comment is functionally empty, so we can just treat
+      // a "Save" as a "delete".
+      return true;
     },
 
     _shouldUndoOnCancel: function() {
-      var new_state = this._getActiveContentState().getWireFormat();
-      var old_state = this._getCommittedContentState().getWireFormat();
-
-      // TODO: This is also simplified.
+      var committed = this._getCommittedContentState();
+      var active = this._getActiveContentState();
+      var initial = this._getInitialContentState();
 
-      var is_empty = this._isVoidContentState(new_state);
-      var is_same = this._isSameContentState(new_state, old_state);
+      // When a user clicks "Cancel", we only offer to let them "Undo" the
+      // action if the undo would be substantive.
 
-      if (!is_empty && !is_same) {
+      // The undo is substantive if the text is nonempty, and not similar to
+      // the last state.
+      var versus = committed || initial;
+      if (!active.isTextEmpty() && !active.isTextSimilar(versus)) {
         return true;
       }
 
+      // The undo is substantive if there's a suggestion, and the suggestion
+      // is not similar to the last state.
+      if (active.getHasSuggestion()) {
+        if (!active.isSuggestionSimilar(versus)) {
+          return true;
+        }
+      }
+
       return false;
     },
 
@@ -887,8 +890,8 @@
       this._applyCall(handler, data);
     },
 
-    _applyDelete: function() {
-      var handler = JX.bind(this, this._ondeleteresponse);
+    _applyDelete: function(prevent_undo) {
+      var handler = JX.bind(this, this._ondeleteresponse, prevent_undo);
 
       var data = this._newRequestData('delete');
 
@@ -903,6 +906,14 @@
       this._applyCall(handler, data);
     },
 
+    _applyEdit: function(state) {
+      var handler = JX.bind(this, this._oneditresponse);
+
+      var data = this._newRequestData('edit', state);
+
+      this._applyCall(handler, data);
+    },
+
     _applyCall: function(handler, data) {
       var uri = this._getInlineURI();
 
@@ -946,31 +957,41 @@
     },
 
     cancel: function() {
+      // NOTE: Read the state before we remove the editor. Otherwise, we might
+      // miss text the user has entered into the textarea.
+      var state = this._getActiveContentState().getWireFormat();
+
       JX.DOM.remove(this._editRow);
       this._editRow = null;
 
-      if (this._shouldDeleteOnCancel()) {
-        this._setPreventUndo(true);
-        this._applyDelete();
-        return;
-      }
+      // When a user clicks "Cancel", we delete the comment if it has never
+      // been saved: we don't have a non-empty display state to revert to.
+      var is_delete = (this._getCommittedContentState() === null);
 
-      if (this._shouldUndoOnCancel()) {
-        var state = this._getActiveContentState().getWireFormat();
-        this._drawUneditRows(state);
-      }
+      var is_undo = this._shouldUndoOnCancel();
 
       // If you "undo" to restore text ("AB") and then "Cancel", we put you
       // back in the original text state ("A"). We also send the original
       // text ("A") to the server as the current persistent state.
 
-      this.setEditing(false);
-      this.setInvisible(false);
+      if (is_undo) {
+        this._drawUneditRows(state);
+      }
 
-      var old_state = this._getCommittedContentState();
-      this._applyCancel(old_state.getWireFormat());
+      if (is_delete) {
+        // NOTE: We're always suppressing the undo from "delete". We want to
+        // use the "undo" we just added above instead, which will get us
+        // back to the ephemeral, client-side editor state.
+        this._applyDelete(true);
+      } else {
+        this.setEditing(false);
+        this.setInvisible(false);
 
-      this._didUpdate(true);
+        var old_state = this._getCommittedContentState();
+        this._applyCancel(old_state.getWireFormat());
+
+        this._didUpdate(true);
+      }
     },
 
     _onCancelResponse: function(response) {
@@ -1067,8 +1088,8 @@
         return null;
       }
 
-      var state = this._getActiveContentState().getWireFormat();
-      if (this._isVoidContentState(state)) {
+      var state = this._getActiveContentState();
+      if (state.isStateEmpty()) {
         return null;
       }
 
@@ -1077,7 +1098,7 @@
         id: this.getID(),
       };
 
-      JX.copy(draft_data, state);
+      JX.copy(draft_data, state.getWireFormat());
 
       return draft_data;
     },
@@ -1193,22 +1214,8 @@
         suggestionText: '',
         hasSuggestion: false
       };
-    },
-
-    _isVoidContentState: function(state) {
-      if (!state.text) {
-        return true;
-      }
-      return (!state.text.length && !state.suggestionText.length);
-    },
-
-    _isSameContentState: function(u, v) {
-      return (
-        ((u === null) === (v === null)) &&
-        (u.text === v.text) &&
-        (u.suggestionText === v.suggestionText) &&
-        (u.hasSuggestion === v.hasSuggestion));
     }
+
   }
 
 });
diff --git a/webroot/rsrc/js/application/diff/DiffInlineContentState.js b/webroot/rsrc/js/application/diff/DiffInlineContentState.js
--- a/webroot/rsrc/js/application/diff/DiffInlineContentState.js
+++ b/webroot/rsrc/js/application/diff/DiffInlineContentState.js
@@ -59,6 +59,72 @@
       return text;
     },
 
+    isStateEmpty: function() {
+      return (this.isTextEmpty() && this.isSuggestionEmpty());
+    },
+
+    isTextEmpty: function() {
+      var text = this.getText();
+      if (text === null) {
+        return true;
+      }
+
+      if (this._isStringSimilar(text, '')) {
+        return true;
+      }
+
+      return false;
+    },
+
+    isSuggestionEmpty: function() {
+      if (!this.getHasSuggestion()) {
+        return true;
+      }
+
+      var suggestion = this.getSuggestionText();
+      if (suggestion === null) {
+        return true;
+      }
+
+      if (this._isStringSimilar(suggestion, '')) {
+        return true;
+      }
+
+      return false;
+    },
+
+    isTextSimilar: function(v) {
+      if (!v) {
+        return false;
+      }
+
+      var us = this.getText();
+      var vs = v.getText();
+
+      return this._isStringSimilar(us, vs);
+    },
+
+    isSuggestionSimilar: function(v) {
+      // If we don't have a comparison state, treat them as dissimilar. This
+      // is expected to occur in old inline comments that did not save an
+      // initial state.
+
+      if (!v) {
+        return false;
+      }
+
+      var us = this.getSuggestionText();
+      var vs = v.getSuggestionText();
+
+      return this._isStringSimilar(us, vs);
+    },
+
+    _isStringSimilar: function(u, v) {
+      u = u || '';
+      v = v || '';
+      return (u === v);
+    },
+
     _getSuggestionNode: function(row) {
       try {
         return JX.DOM.find(row, 'textarea', 'inline-content-suggestion');