diff --git a/src/applications/differential/editor/comment/DifferentialCommentEditor.php b/src/applications/differential/editor/comment/DifferentialCommentEditor.php
index d2690e019f..be49a064a0 100644
--- a/src/applications/differential/editor/comment/DifferentialCommentEditor.php
+++ b/src/applications/differential/editor/comment/DifferentialCommentEditor.php
@@ -273,7 +273,7 @@ class DifferentialCommentEditor {
 
         $current_ccs = $revision->getCCPHIDs();
         if ($current_ccs) {
-          $current_ccs = array_combine($current_ccs, $current_ccs);
+          $current_ccs = array_fill_keys($current_ccs, true);
           foreach ($added_ccs as $k => $cc) {
             if (isset($current_ccs[$cc])) {
               unset($added_ccs[$k]);
@@ -307,9 +307,6 @@ class DifferentialCommentEditor {
         $this->actorPHID);
     }
 
-    // Reload relationships to pick up any reviewer/CC changes.
-    $revision->loadRelationships();
-
     $inline_comments = array();
     if ($this->attachInlineComments) {
       $inline_comments = id(new DifferentialInlineComment())->loadAllWhere(
@@ -341,6 +338,43 @@ class DifferentialCommentEditor {
       }
     }
 
+    // Find any "@mentions" in the comment blocks.
+    $content_blocks = array($comment->getContent());
+    foreach ($inline_comments as $inline) {
+      $content_blocks[] = $inline->getContent();
+    }
+    $mention_ccs = DifferentialMarkupEngineFactory::extractPHIDsFromMentions(
+      $content_blocks);
+    if ($mention_ccs) {
+      $current_ccs = $revision->getCCPHIDs();
+      if ($current_ccs) {
+        $current_ccs = array_fill_keys($current_ccs, true);
+        foreach ($mention_ccs as $key => $mention_cc) {
+          if (isset($current_ccs[$mention_cc])) {
+            unset($mention_ccs);
+          }
+        }
+      }
+      if ($mention_ccs) {
+        $metadata = $comment->getMetadata();
+        $metacc = idx(
+          $metadata,
+          DifferentialComment::METADATA_ADDED_CCS,
+          array());
+        foreach ($mention_ccs as $cc_phid) {
+          DifferentialRevisionEditor::addCC(
+            $revision,
+            $cc_phid,
+            $this->actorPHID);
+          $metacc[] = $cc_phid;
+        }
+        $metadata[DifferentialComment::METADATA_ADDED_CCS] = $metacc;
+
+        $comment->setMetadata($metadata);
+        $comment->save();
+      }
+    }
+
     $phids = array($this->actorPHID);
     $handles = id(new PhabricatorObjectHandleData($phids))
       ->loadHandles();
diff --git a/src/applications/differential/editor/comment/__init__.php b/src/applications/differential/editor/comment/__init__.php
index a11be0084c..74deebcb49 100644
--- a/src/applications/differential/editor/comment/__init__.php
+++ b/src/applications/differential/editor/comment/__init__.php
@@ -10,6 +10,7 @@ phutil_require_module('phabricator', 'applications/differential/constants/action
 phutil_require_module('phabricator', 'applications/differential/constants/revisionstatus');
 phutil_require_module('phabricator', 'applications/differential/editor/revision');
 phutil_require_module('phabricator', 'applications/differential/mail/comment');
+phutil_require_module('phabricator', 'applications/differential/parser/markup');
 phutil_require_module('phabricator', 'applications/differential/storage/changeset');
 phutil_require_module('phabricator', 'applications/differential/storage/comment');
 phutil_require_module('phabricator', 'applications/differential/storage/inlinecomment');
diff --git a/src/applications/differential/editor/revision/DifferentialRevisionEditor.php b/src/applications/differential/editor/revision/DifferentialRevisionEditor.php
index 01ff614cc4..9b9e5b554c 100644
--- a/src/applications/differential/editor/revision/DifferentialRevisionEditor.php
+++ b/src/applications/differential/editor/revision/DifferentialRevisionEditor.php
@@ -600,6 +600,8 @@ class DifferentialRevisionEditor {
           implode(', ', $sql));
       }
     $conn_w->saveTransaction();
+
+    $revision->loadRelationships();
   }
 
 
diff --git a/src/applications/differential/parser/markup/DifferentialMarkupEngineFactory.php b/src/applications/differential/parser/markup/DifferentialMarkupEngineFactory.php
index 959c18fbb8..7116f6050d 100644
--- a/src/applications/differential/parser/markup/DifferentialMarkupEngineFactory.php
+++ b/src/applications/differential/parser/markup/DifferentialMarkupEngineFactory.php
@@ -18,6 +18,23 @@
 
 class DifferentialMarkupEngineFactory {
 
+  public static function extractPHIDsFromMentions(array $content_blocks) {
+    $mentions = array();
+
+    $factory = new DifferentialMarkupEngineFactory();
+    $engine = $factory->newDifferentialCommentMarkupEngine();
+
+    foreach ($content_blocks as $content_block) {
+      $engine->markupText($content_block);
+      $phids = $engine->getTextMetadata(
+        'phabricator.mentioned-user-phids',
+        array());
+      $mentions += $phids;
+    }
+
+    return $mentions;
+  }
+
   public function newDifferentialCommentMarkupEngine() {
     $engine = new PhutilRemarkupEngine();
 
diff --git a/src/infrastructure/markup/remarkup/markuprule/mention/PhabricatorRemarkupRuleMention.php b/src/infrastructure/markup/remarkup/markuprule/mention/PhabricatorRemarkupRuleMention.php
index 0849570767..ccacba0f82 100644
--- a/src/infrastructure/markup/remarkup/markuprule/mention/PhabricatorRemarkupRuleMention.php
+++ b/src/infrastructure/markup/remarkup/markuprule/mention/PhabricatorRemarkupRuleMention.php
@@ -48,10 +48,17 @@ class PhabricatorRemarkupRuleMention
       $user_table->getTableName(),
       $usernames);
 
+    $engine = $this->getEngine();
+    $metadata_key = 'phabricator.mentioned-user-phids';
+    $mentioned = $engine->getTextMetadata($metadata_key, array());
+
     foreach ($real_user_names as $row) {
       $this->actualUsers[strtolower($row['username'])] = $row;
+      $mentioned[$row['phid']] = $row['phid'];
     }
 
+    $engine->setTextMetadata($metadata_key, $mentioned);
+
     return preg_replace_callback(
       $regexp,
       array($this, 'markupMention'),