If/when instance admins on the fediverse decide to ban entire instances from connecting with theirs, they need to do so very responsibly and be 100% open and visible about it. And, I would argue, only in extreme extreme situations this should be done. This practice of banning instances is a very slippery slope and destroys all that the fediverse is.
When users have the power to ban other users and in some cases entire instances, then why on Earth are the admins taking such decisions that affect everyone?
I am sure that if this fediverse will become more popular it will get ruined by such practices. That's why I think the best is to have decentralized networks such as
scuttlebutt.nz/ - that's a proper way of decentralizing. Not creating multiple twitters, but giving up on that idea of "a thing", but rather have people directly connect with other people.