There’s a sequence diagram created by @boyter of the current process:
sequenceDiagram
actor User
User->>Instance Old: Move
Instance Old--)Instance Old: Fetch Followers
loop Every Follower
Instance Old--)Remote Instance: Move
Remote Instance--)Instance Old: Unfollow
Remote Instance--)Instance New: Follow
end
See: https://github.com/boyter/activitypub/blob/8aa3a5418901af9f27878cb00744f4a511c359d6/move-post.md
PS. Also refer to Ideating organization structure for the Grassroots Fediverse (wiki) where the proposal is to unify several documentation efforts.
PPS: Should “Account Migration” become a FEP?