My view on this is... sure why not? The devil is in the details, but the actual code in @robin 's post is a valid as2 actor as far as I can tell. The 'over ATProto' part seems superfluous. From the perspective of an ActivityPub client, it's 'just' an ActivityPub Server + feature detection. It's not clear why the 'over' is necessary, or why it would be 'ActivityPub over ATProto' and not 'ATProto over ActivityPub'. But maybe just better to avoid the preposition altogether.