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
@@ -678,7 +678,6 @@
     'DiffusionCompareController' => 'applications/diffusion/controller/DiffusionCompareController.php',
     'DiffusionConduitAPIMethod' => 'applications/diffusion/conduit/DiffusionConduitAPIMethod.php',
     'DiffusionController' => 'applications/diffusion/controller/DiffusionController.php',
-    'DiffusionCreateCommentConduitAPIMethod' => 'applications/diffusion/conduit/DiffusionCreateCommentConduitAPIMethod.php',
     'DiffusionCreateRepositoriesCapability' => 'applications/diffusion/capability/DiffusionCreateRepositoriesCapability.php',
     'DiffusionDaemonLockException' => 'applications/diffusion/exception/DiffusionDaemonLockException.php',
     'DiffusionDefaultEditCapability' => 'applications/diffusion/capability/DiffusionDefaultEditCapability.php',
@@ -5387,7 +5386,6 @@
     'DiffusionCompareController' => 'DiffusionController',
     'DiffusionConduitAPIMethod' => 'ConduitAPIMethod',
     'DiffusionController' => 'PhabricatorController',
-    'DiffusionCreateCommentConduitAPIMethod' => 'DiffusionConduitAPIMethod',
     'DiffusionCreateRepositoriesCapability' => 'PhabricatorPolicyCapability',
     'DiffusionDaemonLockException' => 'Exception',
     'DiffusionDefaultEditCapability' => 'PhabricatorPolicyCapability',
diff --git a/src/applications/diffusion/conduit/DiffusionCreateCommentConduitAPIMethod.php b/src/applications/diffusion/conduit/DiffusionCreateCommentConduitAPIMethod.php
deleted file mode 100644
--- a/src/applications/diffusion/conduit/DiffusionCreateCommentConduitAPIMethod.php
+++ /dev/null
@@ -1,106 +0,0 @@
-<?php
-
-final class DiffusionCreateCommentConduitAPIMethod
-  extends DiffusionConduitAPIMethod {
-
-  public function getAPIMethodName() {
-    return 'diffusion.createcomment';
-  }
-
-  public function getMethodStatus() {
-    return self::METHOD_STATUS_DEPRECATED;
-  }
-
-  public function getMethodDescription() {
-    return pht(
-      'Add a comment to a Diffusion commit. By specifying an action '.
-      'of "%s", "%s", "%s", or "%s", auditing actions can '.
-      'be triggered. Defaults to "%s".',
-      'concern',
-      'accept',
-      'resign',
-      'close',
-      'comment');
-  }
-
-  protected function defineParamTypes() {
-    return array(
-      'phid'    => 'required string',
-      'action'  => 'optional string',
-      'message' => 'required string',
-      'silent'  => 'optional bool',
-    );
-  }
-
-  protected function defineReturnType() {
-    return 'bool';
-  }
-
-  protected function defineErrorTypes() {
-    return array(
-      'ERR_BAD_COMMIT' => pht('No commit found with that PHID.'),
-      'ERR_BAD_ACTION' => pht('Invalid action type.'),
-      'ERR_MISSING_MESSAGE' => pht('Message is required.'),
-    );
-  }
-
-  protected function execute(ConduitAPIRequest $request) {
-    $commit_phid = $request->getValue('phid');
-    $commit = id(new DiffusionCommitQuery())
-      ->setViewer($request->getUser())
-      ->withPHIDs(array($commit_phid))
-      ->needAuditRequests(true)
-      ->executeOne();
-    if (!$commit) {
-      throw new ConduitException('ERR_BAD_COMMIT');
-    }
-
-    $message = trim($request->getValue('message'));
-    if (!$message) {
-      throw new ConduitException('ERR_MISSING_MESSAGE');
-    }
-
-    $action = $request->getValue('action');
-    if (!$action) {
-      $action = PhabricatorAuditActionConstants::COMMENT;
-    }
-
-    // Disallow ADD_CCS, ADD_AUDITORS forever.
-    if (!in_array($action, array(
-      PhabricatorAuditActionConstants::CONCERN,
-      PhabricatorAuditActionConstants::ACCEPT,
-      PhabricatorAuditActionConstants::COMMENT,
-      PhabricatorAuditActionConstants::RESIGN,
-      PhabricatorAuditActionConstants::CLOSE,
-    ))) {
-      throw new ConduitException('ERR_BAD_ACTION');
-    }
-
-    $xactions = array();
-
-    if ($action != PhabricatorAuditActionConstants::COMMENT) {
-      $xactions[] = id(new PhabricatorAuditTransaction())
-        ->setTransactionType(PhabricatorAuditActionConstants::ACTION)
-        ->setNewValue($action);
-    }
-
-    if (strlen($message)) {
-      $xactions[] = id(new PhabricatorAuditTransaction())
-        ->setTransactionType(PhabricatorTransactions::TYPE_COMMENT)
-        ->attachComment(
-          id(new PhabricatorAuditTransactionComment())
-            ->setCommitPHID($commit->getPHID())
-            ->setContent($message));
-    }
-
-    id(new PhabricatorAuditEditor())
-      ->setActor($request->getUser())
-      ->setContentSource($request->newContentSource())
-      ->setDisableEmail($request->getValue('silent'))
-      ->setContinueOnMissingFields(true)
-      ->applyTransactions($commit, $xactions);
-
-    return true;
-  }
-
-}