They hit r/LemmyMigration and it’s creator once already, right before they announced the Spez AMA. They were quietly unbanned after a while with claims of it being a “mistake”.
I have a feeling they’ll try a much more thorough purge soon, despite all evidence showing how disastrously that would backfire.
It very well could in the future. But the federated model slows it down compared to Reddit et al. where there’s centralized control, at worst a single instance will develop a contained hivemind. If that happens to yours, you can just hop to a new one. If someone is really concerned, they can just spin up their own brand new instance, or fork the code and create something themselves.
I think the other way around is more likely. Their users having normal access in and out, but outsiders having limited access to Meta content. Going for the “exclusive club” vibe and making the users feel “special” will keep most of them in the garden.