Thanks for spotting this - it's actually a bug since it doesn't make sense for that link to be displayed if you're using external user integration.
You can fix it in qa-page-favorites.php by adding:
if (!QA_FINAL_EXTERNAL_USERS)
... before ...
$qa_content['navigation']['sub']=qa_account_sub_navigation();
This fix will be rolled into the Q2A 1.5.1 release. Thanks again!