diff --git a/src/applications/audit/editor/PhabricatorAuditCommentEditor.php b/src/applications/audit/editor/PhabricatorAuditCommentEditor.php
--- a/src/applications/audit/editor/PhabricatorAuditCommentEditor.php
+++ b/src/applications/audit/editor/PhabricatorAuditCommentEditor.php
@@ -76,6 +76,7 @@
 
     // Find any "@mentions" in the content blocks.
     $mention_ccs = PhabricatorMarkupEngine::extractPHIDsFromMentions(
+      $this->getActor(),
       $content_blocks);
     if ($mention_ccs) {
       $metacc = idx(
diff --git a/src/applications/conpherence/conduit/ConduitAPI_conpherence_updatethread_Method.php b/src/applications/conpherence/conduit/ConduitAPI_conpherence_updatethread_Method.php
--- a/src/applications/conpherence/conduit/ConduitAPI_conpherence_updatethread_Method.php
+++ b/src/applications/conpherence/conduit/ConduitAPI_conpherence_updatethread_Method.php
@@ -90,7 +90,10 @@
     if ($message) {
       $xactions = array_merge(
         $xactions,
-        $editor->generateTransactionsFromText($conpherence, $message));
+        $editor->generateTransactionsFromText(
+          $user,
+          $conpherence,
+          $message));
     }
 
     try {
diff --git a/src/applications/conpherence/controller/ConpherenceUpdateController.php b/src/applications/conpherence/controller/ConpherenceUpdateController.php
--- a/src/applications/conpherence/controller/ConpherenceUpdateController.php
+++ b/src/applications/conpherence/controller/ConpherenceUpdateController.php
@@ -55,6 +55,7 @@
         case ConpherenceUpdateActions::MESSAGE:
           $message = $request->getStr('text');
           $xactions = $editor->generateTransactionsFromText(
+            $user,
             $conpherence,
             $message);
           $delete_draft = true;
diff --git a/src/applications/conpherence/editor/ConpherenceEditor.php b/src/applications/conpherence/editor/ConpherenceEditor.php
--- a/src/applications/conpherence/editor/ConpherenceEditor.php
+++ b/src/applications/conpherence/editor/ConpherenceEditor.php
@@ -34,9 +34,9 @@
       $errors[] = self::ERROR_EMPTY_MESSAGE;
     }
 
-    $file_phids =
-      PhabricatorMarkupEngine::extractFilePHIDsFromEmbeddedFiles(
-        array($message));
+    $file_phids = PhabricatorMarkupEngine::extractFilePHIDsFromEmbeddedFiles(
+      $creator,
+      array($message));
     if ($file_phids) {
       $files = id(new PhabricatorFileQuery())
         ->setViewer($creator)
@@ -78,13 +78,14 @@
   }
 
   public function generateTransactionsFromText(
+    PhabricatorUser $viewer,
     ConpherenceThread $conpherence,
     $text) {
 
     $files = array();
-    $file_phids =
-      PhabricatorMarkupEngine::extractFilePHIDsFromEmbeddedFiles(
-        array($text));
+    $file_phids = PhabricatorMarkupEngine::extractFilePHIDsFromEmbeddedFiles(
+      $viewer,
+      array($text));
     // Since these are extracted from text, we might be re-including the
     // same file -- e.g. a mock under discussion. Filter files we
     // already have.
diff --git a/src/applications/conpherence/mail/ConpherenceReplyHandler.php b/src/applications/conpherence/mail/ConpherenceReplyHandler.php
--- a/src/applications/conpherence/mail/ConpherenceReplyHandler.php
+++ b/src/applications/conpherence/mail/ConpherenceReplyHandler.php
@@ -82,6 +82,7 @@
     $xactions = array_merge(
       $xactions,
       $editor->generateTransactionsFromText(
+        $user,
         $conpherence,
         $body));
 
diff --git a/src/applications/maniphest/controller/ManiphestTransactionSaveController.php b/src/applications/maniphest/controller/ManiphestTransactionSaveController.php
--- a/src/applications/maniphest/controller/ManiphestTransactionSaveController.php
+++ b/src/applications/maniphest/controller/ManiphestTransactionSaveController.php
@@ -26,6 +26,7 @@
     // list of all the CCs and then construct a transaction for them at the
     // end if necessary.
     $added_ccs = PhabricatorMarkupEngine::extractPHIDsFromMentions(
+      $user,
       array(
         $request->getStr('comments'),
       ));
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
@@ -973,7 +973,9 @@
     }
 
     $texts = array_mergev($blocks);
-    $phids = PhabricatorMarkupEngine::extractPHIDsFromMentions($texts);
+    $phids = PhabricatorMarkupEngine::extractPHIDsFromMentions(
+      $this->getActor(),
+      $texts);
 
     $this->mentionedPHIDs = $phids;
 
@@ -2173,6 +2175,7 @@
     $phids = array();
     if ($blocks) {
       $phids[] = PhabricatorMarkupEngine::extractFilePHIDsFromEmbeddedFiles(
+        $this->getActor(),
         $blocks);
     }
 
diff --git a/src/infrastructure/markup/PhabricatorMarkupEngine.php b/src/infrastructure/markup/PhabricatorMarkupEngine.php
--- a/src/infrastructure/markup/PhabricatorMarkupEngine.php
+++ b/src/infrastructure/markup/PhabricatorMarkupEngine.php
@@ -494,11 +494,14 @@
     return $engine;
   }
 
-  public static function extractPHIDsFromMentions(array $content_blocks) {
+  public static function extractPHIDsFromMentions(
+    PhabricatorUser $viewer,
+    array $content_blocks) {
+
     $mentions = array();
 
     $engine = self::newDifferentialMarkupEngine();
-    $engine->setConfig('viewer', PhabricatorUser::getOmnipotentUser());
+    $engine->setConfig('viewer', $viewer);
 
     foreach ($content_blocks as $content_block) {
       $engine->markupText($content_block);
@@ -512,11 +515,12 @@
   }
 
   public static function extractFilePHIDsFromEmbeddedFiles(
+    PhabricatorUser $viewer,
     array $content_blocks) {
     $files = array();
 
     $engine = self::newDifferentialMarkupEngine();
-    $engine->setConfig('viewer', PhabricatorUser::getOmnipotentUser());
+    $engine->setConfig('viewer', $viewer);
 
     foreach ($content_blocks as $content_block) {
       $engine->markupText($content_block);