A possible better solution might be to allow the user to create their own group (or super community if you prefer that name) where they can group multiple communities together in a way they see fit (not just necessarily clones of the same community. Examples could be a sports group that allows you to group together communities for all the teams you follow).

This would be beneficial I feel for most users, doesn't affect decentralization, doesn't require a central authority and would be only relevant to each individual user and not applied to anyone else