@erlend@Crell Great questions-- honestly. As-is, "blocks" aren't a feature of ActivityPub or even standardized enough for there to be one spec I could go update, extend or replace-- it's all pretty ad-hoc at the moment, sadly.
In theory, however, a server would have more options open to them: if they want to apply a phpc.social block against anyone with phpc.social in their Actor object, they could! And a block on crell@crellshouse.com would survive you moving to freespeech.social 😏