Mastodon has account migration, though it’s not exactly great. Your old toots refer to your new account but if your old server goes down or deletes your old account, the old content disappears. Followers/subscriptions/lists can be migrated, though.
In theory this can work fine with ActivityPub. What you’d need to do for a migration is to notify every server that has received any of your notes/comments/upvotes of your account’s new location. This can he done by the Move activity, moving your posts to another ActivityPub collection, possibly in conjunction with an Update activity.
You’ll also need to implement some method for every reaction to your post to be associated with the new post, but I think that should work out of the box if you keep your IDs straight.
An account moving between servers in a network of 100 servers, with 400 comments and 2000 upvotes/downvotes, should generate about 240000 requests, 480000 if you require an update to synchronize the new post location (it depends on the ActivityPub implementation I think). At about 1KB of JSON per request, that’s 480 megabytes of network traffic (or 3840 megabits of traffic, or about $0.36 in traffic costs at Amazon’s rates).
I think a straight up account migration may be too much for most Lemmy servers to handle. You’ll probably get rate limited in the process, and the migration will take days or weeks. That means the process needs to be non-standard, probably Lemmy specific, with a Mastodon style redirect fix as a fallback. That would break editing old posts or retracting old votes, though.
A UI designer’s dream is a backend engineer’s nightmare
Without knowing much about Lemmy I would guess that a bit more info is needed, along with some human interaction on both servers to validate the move.
When I signed up i wrote a bit about why I chose that server, I think that as a minimum would also be required.
Edit: I would also only allow moving between servers at the 1st of each month, just to cut down on work for the admins.
Mastodon has account migration, though it’s not exactly great. Your old toots refer to your new account but if your old server goes down or deletes your old account, the old content disappears. Followers/subscriptions/lists can be migrated, though.
In theory this can work fine with ActivityPub. What you’d need to do for a migration is to notify every server that has received any of your notes/comments/upvotes of your account’s new location. This can he done by the Move activity, moving your posts to another ActivityPub collection, possibly in conjunction with an Update activity.
You’ll also need to implement some method for every reaction to your post to be associated with the new post, but I think that should work out of the box if you keep your IDs straight.
An account moving between servers in a network of 100 servers, with 400 comments and 2000 upvotes/downvotes, should generate about 240000 requests, 480000 if you require an update to synchronize the new post location (it depends on the ActivityPub implementation I think). At about 1KB of JSON per request, that’s 480 megabytes of network traffic (or 3840 megabits of traffic, or about $0.36 in traffic costs at Amazon’s rates).
I think a straight up account migration may be too much for most Lemmy servers to handle. You’ll probably get rate limited in the process, and the migration will take days or weeks. That means the process needs to be non-standard, probably Lemmy specific, with a Mastodon style redirect fix as a fallback. That would break editing old posts or retracting old votes, though.