Which is entirely possible to do under ActivityPub. It's baffling to me to think that people can't grasp that servers can, and most likely will, implement serve

Which is entirely possible to do under ActivityPub. It's baffling to me to think that people can't grasp that servers can, and most likely will, implement server level filtering on incoming content. I doubt there's anything that the AT protocol can do to prevent other implementors doing their own thing.