@kaleb@social.coop I've heard it's already possible in ActivityPub even without new delegation functionality, but I've never understood how.

It seems really contrary to the basic model of the system that puts instances at the center of everything, not users. People complain about missing comments in comment threads in part because of that fundamental model, and it's just one sign that account portability across instances would be a tough ask.

I know AP does have cryptographic signatures involved in its operation, so maybe that's part of how it might work. Or I could also imagine bolt on functionality where there would be a home instance and a user using another instance would basically have all traffic forwarded to and from and through the home instance.

But it's hard to imagine a way of cleanly getting around the choice to make instances first class above users.