Also maybe like prioritize interop with the open standard for federation on the internet? ActivityPub is the most widely used federation protocol in the world right now. @Protocol is effectively only for Bluesky.

Isn’t @ freely available if Mastodon etc. want to implement it?

They cover why they didn’t go with ActivityPub pretty clearly in their docs and I think their reasons are pretty good (speaking as someone who came from Mastodon). Pretty sure they will want to finish federation and choosing longterm functions before worrying about interoperability.

With good reason, the Protocol isn’t done. There are good reasons that they choose to build from scratch rather than use ActivityPub https://atproto.com/guides/faq#why-not-use-activitypub