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.
Nothing is stopping anyone from copying content already.
Legal issues - possibly, but then everything you write or do is federated already.