@feld Trying to tackle that, first (actually second, the first one was a brainfart when I tried to handle it in transmogrifier) instinct was to handle it in Federator but that would only work for users that already exist in local DB and thus will do nothing. The problem is the very first thing Pleroma does upon receiving any activity from unknown actor is fetching and saving the actor in ReceiverWorker in order to verify its signature, thus I don't see a way to preemtively filter them without tackling shit onto it.