diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -1723,6 +1723,7 @@
     'PhabricatorMarkupPreviewController' => 'infrastructure/markup/PhabricatorMarkupPreviewController.php',
     'PhabricatorMemeRemarkupRule' => 'applications/macro/markup/PhabricatorMemeRemarkupRule.php',
     'PhabricatorMentionRemarkupRule' => 'applications/people/markup/PhabricatorMentionRemarkupRule.php',
+    'PhabricatorMentionableInterface' => 'applications/transactions/interface/PhabricatorMentionableInterface.php',
     'PhabricatorMercurialGraphStream' => 'applications/repository/daemon/PhabricatorMercurialGraphStream.php',
     'PhabricatorMetaMTAActor' => 'applications/metamta/query/PhabricatorMetaMTAActor.php',
     'PhabricatorMetaMTAActorQuery' => 'applications/metamta/query/PhabricatorMetaMTAActorQuery.php',
@@ -1808,6 +1809,8 @@
     'PhabricatorObjectListQueryTestCase' => 'applications/phid/query/__tests__/PhabricatorObjectListQueryTestCase.php',
     'PhabricatorObjectMailReceiver' => 'applications/metamta/receiver/PhabricatorObjectMailReceiver.php',
     'PhabricatorObjectMailReceiverTestCase' => 'applications/metamta/receiver/__tests__/PhabricatorObjectMailReceiverTestCase.php',
+    'PhabricatorObjectMentionedByObject' => 'applications/transactions/edges/PhabricatorObjectMentionedByObject.php',
+    'PhabricatorObjectMentionsObject' => 'applications/transactions/edges/PhabricatorObjectMentionsObject.php',
     'PhabricatorObjectQuery' => 'applications/phid/query/PhabricatorObjectQuery.php',
     'PhabricatorObjectRemarkupRule' => 'infrastructure/markup/rule/PhabricatorObjectRemarkupRule.php',
     'PhabricatorObjectSelectorDialog' => 'view/control/PhabricatorObjectSelectorDialog.php',
@@ -3084,6 +3087,7 @@
       'PhabricatorSubscribableInterface',
       'PhabricatorCustomFieldInterface',
       'PhabricatorApplicationTransactionInterface',
+      'PhabricatorMentionableInterface',
       'PhabricatorDestructibleInterface',
       'PhabricatorProjectInterface',
     ),
@@ -3698,6 +3702,7 @@
       'PhabricatorPolicyInterface',
       'PhabricatorTokenReceiverInterface',
       'PhabricatorFlaggableInterface',
+      'PhabricatorMentionableInterface',
       'PhrequentTrackableInterface',
       'PhabricatorCustomFieldInterface',
       'PhabricatorDestructibleInterface',
@@ -4658,6 +4663,8 @@
     'PhabricatorObjectListQueryTestCase' => 'PhabricatorTestCase',
     'PhabricatorObjectMailReceiver' => 'PhabricatorMailReceiver',
     'PhabricatorObjectMailReceiverTestCase' => 'PhabricatorTestCase',
+    'PhabricatorObjectMentionedByObject' => 'PhabricatorEdgeType',
+    'PhabricatorObjectMentionsObject' => 'PhabricatorEdgeType',
     'PhabricatorObjectQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorObjectRemarkupRule' => 'PhutilRemarkupRule',
     'PhabricatorOffsetPagedQuery' => 'PhabricatorQuery',
@@ -4693,6 +4700,7 @@
       'PhabricatorSubscribableInterface',
       'PhabricatorTokenReceiverInterface',
       'PhabricatorFlaggableInterface',
+      'PhabricatorMentionableInterface',
       'PhabricatorPolicyInterface',
       'PhabricatorProjectInterface',
     ),
@@ -4908,6 +4916,7 @@
       'PhabricatorFlaggableInterface',
       'PhabricatorTokenReceiverInterface',
       'PhabricatorSubscribableInterface',
+      'PhabricatorMentionableInterface',
       'HarbormasterBuildableInterface',
       'PhabricatorCustomFieldInterface',
       'PhabricatorApplicationTransactionInterface',
diff --git a/src/applications/differential/editor/DifferentialTransactionEditor.php b/src/applications/differential/editor/DifferentialTransactionEditor.php
--- a/src/applications/differential/editor/DifferentialTransactionEditor.php
+++ b/src/applications/differential/editor/DifferentialTransactionEditor.php
@@ -1271,8 +1271,10 @@
         ->execute();
 
       if ($tasks) {
+        $phid_map = mpull($tasks, 'getPHID', 'getPHID');
         $edge_related = DifferentialRevisionHasTaskEdgeType::EDGECONST;
-        $edges[$edge_related] = mpull($tasks, 'getPHID', 'getPHID');
+        $edges[$edge_related] = $phid_map;
+        $this->setUnmentionablePHIDMap($phid_map);
       }
     }
 
diff --git a/src/applications/differential/storage/DifferentialRevision.php b/src/applications/differential/storage/DifferentialRevision.php
--- a/src/applications/differential/storage/DifferentialRevision.php
+++ b/src/applications/differential/storage/DifferentialRevision.php
@@ -10,6 +10,7 @@
     PhabricatorSubscribableInterface,
     PhabricatorCustomFieldInterface,
     PhabricatorApplicationTransactionInterface,
+    PhabricatorMentionableInterface,
     PhabricatorDestructibleInterface,
     PhabricatorProjectInterface {
 
diff --git a/src/applications/maniphest/storage/ManiphestTask.php b/src/applications/maniphest/storage/ManiphestTask.php
--- a/src/applications/maniphest/storage/ManiphestTask.php
+++ b/src/applications/maniphest/storage/ManiphestTask.php
@@ -6,6 +6,7 @@
     PhabricatorPolicyInterface,
     PhabricatorTokenReceiverInterface,
     PhabricatorFlaggableInterface,
+    PhabricatorMentionableInterface,
     PhrequentTrackableInterface,
     PhabricatorCustomFieldInterface,
     PhabricatorDestructibleInterface,
diff --git a/src/applications/paste/storage/PhabricatorPaste.php b/src/applications/paste/storage/PhabricatorPaste.php
--- a/src/applications/paste/storage/PhabricatorPaste.php
+++ b/src/applications/paste/storage/PhabricatorPaste.php
@@ -5,6 +5,7 @@
     PhabricatorSubscribableInterface,
     PhabricatorTokenReceiverInterface,
     PhabricatorFlaggableInterface,
+    PhabricatorMentionableInterface,
     PhabricatorPolicyInterface,
     PhabricatorProjectInterface {
 
diff --git a/src/applications/repository/storage/PhabricatorRepositoryCommit.php b/src/applications/repository/storage/PhabricatorRepositoryCommit.php
--- a/src/applications/repository/storage/PhabricatorRepositoryCommit.php
+++ b/src/applications/repository/storage/PhabricatorRepositoryCommit.php
@@ -7,6 +7,7 @@
     PhabricatorFlaggableInterface,
     PhabricatorTokenReceiverInterface,
     PhabricatorSubscribableInterface,
+    PhabricatorMentionableInterface,
     HarbormasterBuildableInterface,
     PhabricatorCustomFieldInterface,
     PhabricatorApplicationTransactionInterface {
diff --git a/src/applications/transactions/edges/PhabricatorObjectMentionedByObject.php b/src/applications/transactions/edges/PhabricatorObjectMentionedByObject.php
new file mode 100644
--- /dev/null
+++ b/src/applications/transactions/edges/PhabricatorObjectMentionedByObject.php
@@ -0,0 +1,26 @@
+<?php
+
+final class PhabricatorObjectMentionedByObject extends PhabricatorEdgeType {
+
+  const EDGECONST = 43;
+
+  public function getInverseEdgeConstant() {
+    return PhabricatorObjectMentionsObject::EDGECONST;
+  }
+
+  public function shouldWriteInverseTransactions() {
+    return true;
+  }
+
+  public function getTransactionAddString(
+    $actor,
+    $add_count,
+    $add_edges) {
+
+    return pht(
+      '%s mentioned this in %s.',
+      $actor,
+      $add_edges);
+  }
+
+}
diff --git a/src/applications/transactions/edges/PhabricatorObjectMentionsObject.php b/src/applications/transactions/edges/PhabricatorObjectMentionsObject.php
new file mode 100644
--- /dev/null
+++ b/src/applications/transactions/edges/PhabricatorObjectMentionsObject.php
@@ -0,0 +1,15 @@
+<?php
+
+final class PhabricatorObjectMentionsObject extends PhabricatorEdgeType {
+
+  const EDGECONST = 44;
+
+  public function getInverseEdgeConstant() {
+    return PhabricatorObjectMentionedByObject::EDGECONST;
+  }
+
+  public function shouldWriteInverseTransactions() {
+    return true;
+  }
+
+}
diff --git a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
--- a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -21,6 +21,7 @@
   private $heraldAdapter;
   private $heraldTranscript;
   private $subscribers;
+  private $unmentionablePHIDMap = array();
 
   private $isPreview;
   private $isHeraldEditor;
@@ -175,6 +176,15 @@
     return $this->disableEmail;
   }
 
+  public function setUnmentionablePHIDMap($map) {
+    $this->unmentionablePHIDMap = $map;
+    return $this;
+  }
+
+  public function getUnmentionablePHIDMap() {
+    return $this->unmentionablePHIDMap;
+  }
+
   public function getTransactionTypes() {
     $types = array();
 
@@ -1013,7 +1023,7 @@
     }
   }
 
-  private function buildMentionTransaction(
+  private function buildSubscribeTransaction(
     PhabricatorLiskDAO $object,
     array $xactions,
     array $blocks) {
@@ -1119,12 +1129,12 @@
       $blocks[$key] = $this->getRemarkupBlocksFromTransaction($xaction);
     }
 
-    $mention_xaction = $this->buildMentionTransaction(
+    $subscribe_xaction = $this->buildSubscribeTransaction(
       $object,
       $xactions,
       $blocks);
-    if ($mention_xaction) {
-      $xactions[] = $mention_xaction;
+    if ($subscribe_xaction) {
+      $xactions[] = $subscribe_xaction;
     }
 
     // TODO: For now, this is just a placeholder.
@@ -1156,17 +1166,22 @@
       $blocks,
       $engine);
 
-    if ($object instanceof PhabricatorProjectInterface) {
-      $phids = array();
-      foreach ($blocks as $key => $xaction_blocks) {
-        foreach ($xaction_blocks as $block) {
-          $engine->markupText($block);
-          $phids += $engine->getTextMetadata(
-            PhabricatorObjectRemarkupRule::KEY_MENTIONED_OBJECTS,
-            array());
-        }
+    $mentioned_phids = array();
+    foreach ($blocks as $key => $xaction_blocks) {
+      foreach ($xaction_blocks as $block) {
+        $engine->markupText($block);
+        $mentioned_phids += $engine->getTextMetadata(
+          PhabricatorObjectRemarkupRule::KEY_MENTIONED_OBJECTS,
+          array());
       }
+    }
+
+    if (!$mentioned_phids) {
+      return $block_xactions;
+    }
 
+    if ($object instanceof PhabricatorProjectInterface) {
+      $phids = $mentioned_phids;
       $project_type = PhabricatorProjectProjectPHIDType::TYPECONST;
       foreach ($phids as $key => $phid) {
         if (phid_get_type($phid) != $project_type) {
@@ -1184,6 +1199,29 @@
       }
     }
 
+    $objects = id(new PhabricatorObjectQuery())
+      ->setViewer($this->getActor())
+      ->withPHIDs($mentioned_phids)
+      ->execute();
+
+    $mentionable_phids = array();
+    foreach ($objects as $object) {
+      if ($object instanceof PhabricatorMentionableInterface) {
+        if (idx($this->getUnmentionablePHIDMap(), $object->getPHID())) {
+          continue;
+        }
+        $mentionable_phids[$object->getPHID()] = $object->getPHID();
+      }
+    }
+    if ($mentionable_phids) {
+      $edge_type = PhabricatorObjectMentionsObject::EDGECONST;
+      $block_xactions[] = newv(get_class(head($xactions)), array())
+        ->setIgnoreOnNoEffect(true)
+        ->setTransactionType(PhabricatorTransactions::TYPE_EDGE)
+        ->setMetadataValue('edge:type', $edge_type)
+        ->setNewValue(array('+' => $mentionable_phids));
+    }
+
     return $block_xactions;
   }
 
diff --git a/src/applications/transactions/interface/PhabricatorMentionableInterface.php b/src/applications/transactions/interface/PhabricatorMentionableInterface.php
new file mode 100644
--- /dev/null
+++ b/src/applications/transactions/interface/PhabricatorMentionableInterface.php
@@ -0,0 +1,12 @@
+<?php
+
+/**
+ * Allow infrastructure to automagically create "mentioned" transactions
+ * - actually TYPE_EDGE transactions that add "mentioned" edges - to the
+ * implementing object.
+ */
+interface PhabricatorMentionableInterface {
+
+  public function getPHID();
+
+}
diff --git a/src/applications/transactions/storage/PhabricatorApplicationTransaction.php b/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
--- a/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
+++ b/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
@@ -438,6 +438,19 @@
         if ($field) {
           return $field->shouldHideInApplicationTransactions($this);
         }
+      case PhabricatorTransactions::TYPE_EDGE:
+        $edge_type = $this->getMetadataValue('edge:type');
+        switch ($edge_type) {
+          case PhabricatorObjectMentionsObject::EDGECONST:
+            return true;
+            break;
+          case PhabricatorObjectMentionedByObject::EDGECONST:
+            return false;
+            break;
+          default:
+            break;
+        }
+        break;
     }
 
     return false;
@@ -456,6 +469,17 @@
             return false;
         }
         return true;
+     case PhabricatorTransactions::TYPE_EDGE:
+        $edge_type = $this->getMetadataValue('edge:type');
+        switch ($edge_type) {
+          case PhabricatorObjectMentionsObject::EDGECONST:
+          case PhabricatorObjectMentionedByObject::EDGECONST:
+            return true;
+            break;
+          default:
+            break;
+        }
+        break;
     }
 
     return $this->shouldHide();
@@ -475,6 +499,17 @@
             return false;
         }
         return true;
+     case PhabricatorTransactions::TYPE_EDGE:
+        $edge_type = $this->getMetadataValue('edge:type');
+        switch ($edge_type) {
+          case PhabricatorObjectMentionsObject::EDGECONST:
+          case PhabricatorObjectMentionedByObject::EDGECONST:
+            return true;
+            break;
+          default:
+            break;
+        }
+        break;
     }
 
     return $this->shouldHide();