“possible duplicate” comment should be re-added if it’s been deleted
The vote is now there, however the expected "possible duplicate of..." comment was never added.
By the time I voted to close, there was no link whatsoever to the dupe question, unless it's in a deleted comment I can't see. (Now there is but it was posted after my vote)
My only assumption as this point is that it's due to the question being migrated but it might also be "global" bug.