The Fediverse is simply a term for all of the instances. It's not entirely fragmented, there is certainly shared hosts between bubbles in the fediverse. Though

The Fediverse is simply a term for all of the instances. It's not entirely fragmented, there is certainly shared hosts between bubbles in the fediverse. Though I don't think this is an issue really; our own universe functions on the bubble principle as well and it makes fediverse a place that you can find an instance to be on without having to worry that your instance moderator will allow nazis to vent their garbage into your feed.