diff --git a/src/applications/differential/controller/DifferentialChangesetViewController.php b/src/applications/differential/controller/DifferentialChangesetViewController.php
--- a/src/applications/differential/controller/DifferentialChangesetViewController.php
+++ b/src/applications/differential/controller/DifferentialChangesetViewController.php
@@ -109,28 +109,7 @@
     }
 
     if ($left) {
-      $left_data = $left->makeNewFile();
-      $left_properties = $left->getNewProperties();
-      if ($right) {
-        $right_data = $right->makeNewFile();
-        $right_properties = $right->getNewProperties();
-      } else {
-        $right_data = $left->makeOldFile();
-        $right_properties = $left->getOldProperties();
-      }
-
-      $engine = new PhabricatorDifferenceEngine();
-      $synthetic = $engine->generateChangesetFromFileContent(
-        $left_data,
-        $right_data);
-
-      $choice = clone nonempty($left, $right);
-      $choice->attachHunks($synthetic->getHunks());
-
-      $choice->setOldProperties($left_properties);
-      $choice->setNewProperties($right_properties);
-
-      $changeset = $choice;
+      $changeset = $left->newComparisonChangeset($right);
     }
 
     if ($left_new || $right_new) {
diff --git a/src/applications/differential/parser/DifferentialChangesetParser.php b/src/applications/differential/parser/DifferentialChangesetParser.php
--- a/src/applications/differential/parser/DifferentialChangesetParser.php
+++ b/src/applications/differential/parser/DifferentialChangesetParser.php
@@ -1694,27 +1694,10 @@
     $changeset = $this->changeset;
     $viewer = $this->getViewer();
 
-    // TODO: This should probably be made non-optional in the future.
-    if (!$viewer) {
-      return null;
-    }
-
-    $old_file = null;
-    $new_file = null;
-
-    switch ($changeset->getFileType()) {
-      case DifferentialChangeType::FILE_IMAGE:
-      case DifferentialChangeType::FILE_BINARY:
-        list($old_file, $new_file) = $this->loadFileObjectsForChangeset();
-        break;
-    }
-
-    $type_delete = DifferentialChangeType::TYPE_DELETE;
-    $type_add = DifferentialChangeType::TYPE_ADD;
-    $change_type = $changeset->getChangeType();
+    list($old_file, $new_file) = $this->loadFileObjectsForChangeset();
 
-    $no_old = ($change_type == $type_add);
-    $no_new = ($change_type == $type_delete);
+    $no_old = !$changeset->hasOldState();
+    $no_new = !$changeset->hasNewState();
 
     if ($no_old) {
       $old_ref = null;
@@ -1742,7 +1725,6 @@
       }
     }
 
-
     $old_engines = null;
     if ($old_ref) {
       $old_engines = PhabricatorDocumentEngine::getEnginesForRef(
@@ -1813,44 +1795,12 @@
     $changeset = $this->changeset;
     $viewer = $this->getViewer();
 
+    $old_phid = $changeset->getOldFileObjectPHID();
+    $new_phid = $changeset->getNewFileObjectPHID();
+
     $old_file = null;
     $new_file = null;
 
-    // TODO: Improve the architectural issue as discussed in D955
-    // https://secure.phabricator.com/D955
-    $reference = $this->getRenderingReference();
-    $parts = explode('/', $reference);
-    if (count($parts) == 2) {
-      list($id, $vs) = $parts;
-    } else {
-      $id = $parts[0];
-      $vs = 0;
-    }
-    $id = (int)$id;
-    $vs = (int)$vs;
-
-    if (!$vs) {
-      $metadata = $this->changeset->getMetadata();
-      $old_phid = idx($metadata, 'old:binary-phid');
-      $new_phid = idx($metadata, 'new:binary-phid');
-    } else {
-      $vs_changeset = id(new DifferentialChangeset())->load($vs);
-      $old_phid = null;
-      $new_phid = null;
-
-      // TODO: This is spooky, see D6851
-      if ($vs_changeset) {
-        $vs_metadata = $vs_changeset->getMetadata();
-        $old_phid = idx($vs_metadata, 'new:binary-phid');
-      }
-
-      $changeset = id(new DifferentialChangeset())->load($id);
-      if ($changeset) {
-        $metadata = $changeset->getMetadata();
-        $new_phid = idx($metadata, 'new:binary-phid');
-      }
-    }
-
     if ($old_phid || $new_phid) {
       $file_phids = array();
       if ($old_phid) {
@@ -1864,13 +1814,28 @@
         ->setViewer($viewer)
         ->withPHIDs($file_phids)
         ->execute();
+      $files = mpull($files, null, 'getPHID');
+
+      if ($old_phid) {
+        $old_file = idx($files, $old_phid);
+        if (!$old_file) {
+          throw new Exception(
+            pht(
+              'Failed to load file data for changeset ("%s").',
+              $old_phid));
+        }
+        $changeset->attachOldFileObject($old_file);
+      }
 
-      foreach ($files as $file) {
-        if ($file->getPHID() == $old_phid) {
-          $old_file = $file;
-        } else if ($file->getPHID() == $new_phid) {
-          $new_file = $file;
+      if ($new_phid) {
+        $new_file = idx($files, $new_phid);
+        if (!$new_file) {
+          throw new Exception(
+            pht(
+              'Failed to load file data for changeset ("%s").',
+              $new_phid));
         }
+        $changeset->attachNewFileObject($new_file);
       }
     }
 
diff --git a/src/applications/differential/render/DifferentialChangesetRenderer.php b/src/applications/differential/render/DifferentialChangesetRenderer.php
--- a/src/applications/differential/render/DifferentialChangesetRenderer.php
+++ b/src/applications/differential/render/DifferentialChangesetRenderer.php
@@ -647,16 +647,26 @@
     $old = $changeset->getOldProperties();
     $new = $changeset->getNewProperties();
 
-    // When adding files, don't show the uninteresting 644 filemode change.
-    if ($changeset->getChangeType() == DifferentialChangeType::TYPE_ADD &&
-        $new == array('unix:filemode' => '100644')) {
-      unset($new['unix:filemode']);
-    }
+    // If a property has been changed, but is not present on one side of the
+    // change and has an uninteresting default value on the other, remove it.
+    // This most commonly happens when a change adds or removes a file: the
+    // side of the change with the file has a "100644" filemode in Git.
+
+    $defaults = array(
+      'unix:filemode' => '100644',
+    );
 
-    // Likewise when removing files.
-    if ($changeset->getChangeType() == DifferentialChangeType::TYPE_DELETE &&
-        $old == array('unix:filemode' => '100644')) {
-      unset($old['unix:filemode']);
+    foreach ($defaults as $default_key => $default_value) {
+      $old_value = idx($old, $default_key, $default_value);
+      $new_value = idx($new, $default_key, $default_value);
+
+      $old_default = ($old_value === $default_value);
+      $new_default = ($new_value === $default_value);
+
+      if ($old_default && $new_default) {
+        unset($old[$default_key]);
+        unset($new[$default_key]);
+      }
     }
 
     $metadata = $changeset->getMetadata();
diff --git a/src/applications/differential/storage/DifferentialChangeset.php b/src/applications/differential/storage/DifferentialChangeset.php
--- a/src/applications/differential/storage/DifferentialChangeset.php
+++ b/src/applications/differential/storage/DifferentialChangeset.php
@@ -28,6 +28,11 @@
   private $newFileObject = self::ATTACHABLE;
   private $oldFileObject = self::ATTACHABLE;
 
+  private $hasOldState;
+  private $hasNewState;
+  private $oldStateMetadata;
+  private $newStateMetadata;
+
   const TABLE_CACHE = 'differential_changeset_parse_cache';
 
   const METADATA_TRUSTED_ATTRIBUTES = 'attributes.trusted';
@@ -134,6 +139,34 @@
     return $this->changesetPackages;
   }
 
+  public function setHasOldState($has_old_state) {
+    $this->hasOldState = $has_old_state;
+    return $this;
+  }
+
+  public function setHasNewState($has_new_state) {
+    $this->hasNewState = $has_new_state;
+    return $this;
+  }
+
+  public function hasOldState() {
+    if ($this->hasOldState !== null) {
+      return $this->hasOldState;
+    }
+
+    $change_type = $this->getChangeType();
+    return !DifferentialChangeType::isCreateChangeType($change_type);
+  }
+
+  public function hasNewState() {
+    if ($this->hasNewState !== null) {
+      return $this->hasNewState;
+    }
+
+    $change_type = $this->getChangeType();
+    return !DifferentialChangeType::isDeleteChangeType($change_type);
+  }
+
   public function save() {
     $this->openTransaction();
       $ret = parent::save();
@@ -490,6 +523,110 @@
     return $this->assertAttached($this->oldFileObject);
   }
 
+  public function newComparisonChangeset(
+    DifferentialChangeset $against = null) {
+
+    $left = $this;
+    $right = $against;
+
+    $left_data = $left->makeNewFile();
+    $left_properties = $left->getNewProperties();
+    $left_metadata = $left->getNewStateMetadata();
+    $left_state = $left->hasNewState();
+    $shared_metadata = $left->getMetadata();
+    if ($right) {
+      $right_data = $right->makeNewFile();
+      $right_properties = $right->getNewProperties();
+      $right_metadata = $right->getNewStateMetadata();
+      $right_state = $right->hasNewState();
+      $shared_metadata = $right->getMetadata();
+    } else {
+      $right_data = $left->makeOldFile();
+      $right_properties = $left->getOldProperties();
+      $right_metadata = $left->getOldStateMetadata();
+      $right_state = $left->hasOldState();
+    }
+
+    $engine = new PhabricatorDifferenceEngine();
+
+    $synthetic = $engine->generateChangesetFromFileContent(
+      $left_data,
+      $right_data);
+
+    $comparison = id(new self())
+      ->makeEphemeral(true)
+      ->attachDiff($left->getDiff())
+      ->setOldFile($left->getFilename())
+      ->setFilename($right->getFilename());
+
+    // TODO: Change type?
+    // TODO: File type?
+    // TODO: Away paths?
+    // TODO: View state key?
+
+    $comparison->attachHunks($synthetic->getHunks());
+
+    $comparison->setOldProperties($left_properties);
+    $comparison->setNewProperties($right_properties);
+
+    $comparison
+      ->setOldStateMetadata($left_metadata)
+      ->setNewStateMetadata($right_metadata)
+      ->setHasOldState($left_state)
+      ->setHasNewState($right_state);
+
+    // NOTE: Some metadata is not stored statefully, like the "generated"
+    // flag. For now, use the rightmost "new state" metadata to fill in these
+    // values.
+
+    $metadata = $comparison->getMetadata();
+    $metadata = $metadata + $shared_metadata;
+    $comparison->setMetadata($metadata);
+
+    return $comparison;
+  }
+
+  public function getNewStateMetadata() {
+    return $this->getMetadataWithPrefix('new:');
+  }
+
+  public function setNewStateMetadata(array $metadata) {
+    return $this->setMetadataWithPrefix($metadata, 'new:');
+  }
+
+  public function getOldStateMetadata() {
+    return $this->getMetadataWithPrefix('old:');
+  }
+
+  public function setOldStateMetadata(array $metadata) {
+    return $this->setMetadataWithPrefix($metadata, 'old:');
+  }
+
+  private function getMetadataWithPrefix($prefix) {
+    $length = strlen($prefix);
+
+    $result = array();
+    foreach ($this->getMetadata() as $key => $value) {
+      if (strncmp($key, $prefix, $length)) {
+        continue;
+      }
+
+      $key = substr($key, $length);
+      $result[$key] = $value;
+    }
+
+    return $result;
+  }
+
+  private function setMetadataWithPrefix(array $metadata, $prefix) {
+    foreach ($metadata as $key => $value) {
+      $key = $prefix.$key;
+      $this->metadata[$key] = $value;
+    }
+
+    return $this;
+  }
+
 
 /* -(  PhabricatorPolicyInterface  )----------------------------------------- */