Idea: if you mod a community on a lemmy.somewhere you should be able to migrate it to lemmy.elsewhere which would include all post & comment links being forwarded and subbed users having their subscription updated to reflect the new location.
I’m aware this would be a way down the road as user account migration alone is still not great but it would be a great feature for the fediverse to have to avoid centralisation and mod/server admin wars.
I think it should be a “copy community” feature, then mods can just prevent posts in the old community and make a sticky that points to the new location.
Making users automatically subscribe to a community on a different instance (even if it’s “the same community”) is pushing it a bit in terms of moderator power. Also makes things worse in terms of exploits and others have pointed out.
Mastodon uses aliasing for account migration. Your old account still exists on the original server, but it points to your new account. Following the old account automatically reroutes the follow to the new one. This could be done at the group level for lemmy without needing to manually lock the original group or ask users to find the new one.
The issue is that users might object to subscribing to a community on a particular instance. I guess it’s not the end of the world, you can always unsubscribe but I can imagine some people being very upset to be associated with certain politically leaning instances or worse.
Perhaps a notification when it occurs, so you could unsubscribe if you wish.
Have something like a mass message to subscribers with a link to the new instance.
Then the old instance owner can take the old community name back.