diff --git a/src/applications/diffusion/query/DiffusionResolveUserQuery.php b/src/applications/diffusion/query/DiffusionResolveUserQuery.php
--- a/src/applications/diffusion/query/DiffusionResolveUserQuery.php
+++ b/src/applications/diffusion/query/DiffusionResolveUserQuery.php
@@ -8,25 +8,14 @@
 final class DiffusionResolveUserQuery extends Phobject {
 
   private $name;
-  private $commit;
 
   public function withName($name) {
     $this->name = $name;
     return $this;
   }
 
-  public function withCommit($commit) {
-    $this->commit = $commit;
-    return $this;
-  }
-
   public function execute() {
-    $user_name = $this->name;
-
-    $phid = $this->findUserPHID($this->name);
-    $phid = $this->fireLookupEvent($phid);
-
-    return $phid;
+    return $this->findUserPHID($this->name);
   }
 
   private function findUserPHID($user_name) {
@@ -75,33 +64,15 @@
   }
 
 
-  /**
-   * Emit an event so installs can do custom lookup of commit authors who may
-   * not be naturally resolvable.
-   */
-  private function fireLookupEvent($guess) {
-
-    $type = PhabricatorEventType::TYPE_DIFFUSION_LOOKUPUSER;
-    $data = array(
-      'commit'  => $this->commit,
-      'query'   => $this->name,
-      'result'  => $guess,
-    );
-
-    $event = new PhabricatorEvent($type, $data);
-    PhutilEventEngine::dispatchEvent($event);
-
-    return $event->getValue('result');
-  }
-
-
   private function findUserByUserName($user_name) {
     $by_username = id(new PhabricatorUser())->loadOneWhere(
       'userName = %s',
       $user_name);
+
     if ($by_username) {
       return $by_username->getPHID();
     }
+
     return null;
   }
 
@@ -112,18 +83,22 @@
     $by_realname = id(new PhabricatorUser())->loadAllWhere(
       'realName = %s',
       $real_name);
+
     if (count($by_realname) == 1) {
-      return reset($by_realname)->getPHID();
+      return head($by_realname)->getPHID();
     }
+
     return null;
   }
 
 
   private function findUserByEmailAddress($email_address) {
     $by_email = PhabricatorUser::loadOneWithEmailAddress($email_address);
+
     if ($by_email) {
       return $by_email->getPHID();
     }
+
     return null;
   }
 
diff --git a/src/applications/repository/management/PhabricatorRepositoryManagementLookupUsersWorkflow.php b/src/applications/repository/management/PhabricatorRepositoryManagementLookupUsersWorkflow.php
--- a/src/applications/repository/management/PhabricatorRepositoryManagementLookupUsersWorkflow.php
+++ b/src/applications/repository/management/PhabricatorRepositoryManagementLookupUsersWorkflow.php
@@ -99,7 +99,6 @@
 
   private function resolveUser(PhabricatorRepositoryCommit $commit, $name) {
     $phid = id(new DiffusionResolveUserQuery())
-      ->withCommit($commit)
       ->withName($name)
       ->execute();
 
diff --git a/src/applications/repository/management/PhabricatorRepositoryManagementRebuildIdentitiesWorkflow.php b/src/applications/repository/management/PhabricatorRepositoryManagementRebuildIdentitiesWorkflow.php
--- a/src/applications/repository/management/PhabricatorRepositoryManagementRebuildIdentitiesWorkflow.php
+++ b/src/applications/repository/management/PhabricatorRepositoryManagementRebuildIdentitiesWorkflow.php
@@ -101,7 +101,6 @@
     if (empty($seen[$identity_key])) {
       try {
         $user_phid = id(new DiffusionResolveUserQuery())
-          ->withCommit($commit)
           ->withName($identity_name)
           ->execute();
 
diff --git a/src/applications/repository/worker/commitmessageparser/PhabricatorRepositoryCommitMessageParserWorker.php b/src/applications/repository/worker/commitmessageparser/PhabricatorRepositoryCommitMessageParserWorker.php
--- a/src/applications/repository/worker/commitmessageparser/PhabricatorRepositoryCommitMessageParserWorker.php
+++ b/src/applications/repository/worker/commitmessageparser/PhabricatorRepositoryCommitMessageParserWorker.php
@@ -182,7 +182,6 @@
     $user_name) {
 
     return id(new DiffusionResolveUserQuery())
-      ->withCommit($commit)
       ->withName($user_name)
       ->execute();
   }
diff --git a/src/docs/user/userguide/events.diviner b/src/docs/user/userguide/events.diviner
--- a/src/docs/user/userguide/events.diviner
+++ b/src/docs/user/userguide/events.diviner
@@ -159,35 +159,6 @@
   - `repository` The @{class:PhabricatorRepository} the commit was discovered
     in.
 
-== Diffusion: Lookup User ==
-
-The constant for this event is
-`PhabricatorEventType::TYPE_DIFFUSION_LOOKUPUSER`.
-
-This event is dispatched when the daemons are trying to link a commit to a
-Phabricator user account. You can listen for it to improve the accuracy of
-associating users with their commits.
-
-By default, Phabricator will try to find matches based on usernames, real names,
-or email addresses, but this can result in incorrect matches (e.g., if you have
-several employees with the same name) or failures to match (e.g., if someone
-changed their email address). Listening for this event allows you to intercept
-the lookup and supplement the results from another datasource.
-
-Data available on this event:
-
-  - `commit` The @{class:PhabricatorRepositoryCommit} that data is being looked
-    up for.
-  - `query` The author or committer string being looked up. This will usually
-    be something like "Abraham Lincoln <alincoln@logcabin.example.com>", but
-    comes from the commit metadata so it may not be well-formatted.
-  - `result` The current result from the lookup (Phabricator's best guess at
-    the user PHID of the user named in the "query"). To substitute the result
-    with a different result, replace this with the correct PHID in your event
-    listener.
-
-Using @{class@libphutil:PhutilEmailAddress} may be helpful in parsing the query.
-
 == Test: Did Run Test ==
 
 The constant for this event is
diff --git a/src/infrastructure/events/constant/PhabricatorEventType.php b/src/infrastructure/events/constant/PhabricatorEventType.php
--- a/src/infrastructure/events/constant/PhabricatorEventType.php
+++ b/src/infrastructure/events/constant/PhabricatorEventType.php
@@ -9,7 +9,6 @@
   const TYPE_DIFFERENTIAL_WILLMARKGENERATED = 'differential.willMarkGenerated';
 
   const TYPE_DIFFUSION_DIDDISCOVERCOMMIT    = 'diffusion.didDiscoverCommit';
-  const TYPE_DIFFUSION_LOOKUPUSER           = 'diffusion.lookupUser';
 
   const TYPE_TEST_DIDRUNTEST                = 'test.didRunTest';