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.
But that also makes it incredibly easy for communities on defederated servers to set up shop elsewhere.
And those communities may be the sole reason that the server was defederated in the first place.
I think a possible outcome is that the larger instances would have to put a stop to open creation of new communities, to prevent toxic groups from setting up shop and moving all their objectionable content and users into the space.
I think it can be solved with a two step process. First, the mods of the community and only them can make a request to move from instance A to instance B, and second, the admins or mods of instance B approve the request, importing only the posts and comments from federated users.