@robin @volkris cool we both want that. ATP isn't needed for those (not saying it can't be shoehorned in).
Using DID URIs with ActivityPub, which is already allowed by the protocol, is what makes it possible. `did:plc` is one very opionated DID method, but imho there's no reason to constrain to it. End-users and implementation operators are in the best position to pick their supported did method, not protocol designers.
Protocol designers can design for the did-method-agnostic DID abstraction.