[vidarh]

The recovery key bit is the one part I actually like.

But improving on the ActivityPub user migration store is also a minor/trivial change away from doing much better than today: you just need to change ActivityPub Ids to either fully a contentadressable hash or referencing a base that is under user control, plus a revocation key style mechanism for letting the user sign claims about their identity in order to allow unilateral moves.