Actually, no it isn't.

The known alts thread is for reporting alts that have been uncovered.

Where the scammers try to counter with FUD is using the myth that it (the thread) is to solely tag scammers.

The irony is you want people to tag your old UID but you don't want to report it to to the very people you are concerned will tag it.

Can you prove the old UID is yours so we're not just tagging someone so you can get off on the grief it would cause?