On our install, we have an LDAP auth provider enabled but we do not allow registration through it. Instead we manually import users as needed. Whenever a user logs in with their LDAP account before I have imported them, a "ghost" user with their username gets added to the external accounts table even though they themselves do not have a phabricator user account yet (and are correctly prevented from logging in). This entry in the external accounts table prevents me from being able to import their account through the LDAP importer. Each time this happens I have to manually go delete that row from the external accounts table in order to import their account through LDAP.