Mjolnir is designed to apply decentralised public blocklists - i.e. you pick which banlists to apply; there are a bunch published by different people (matrix.org, the matrix 'community moderation effort', etc). Admittedly moderators do share lists (so that if #archlinux bans you, others might pick up the ban), but there's no intrinsic centralisation.
BlueSky also has this, but it works poorly because people use blocklists as a form of harassment, or else take over existing lists and add their enemies to it.
Eh, not really. It really is decentralized, you can find them on Google. They could stop respecting a certain list but I think you can host your own AppView and get it back?
No one is successfully hosting their own AppView at this point. Blacksky had one but had to roll it back. Northsky has it as their priority, but they don't have one yet.
I mean when lists are opt-in and users have to specifically choose what lists to subscribe to then well… kinda tough shit if you end up on one that many people are happy with. That's the point of putting moderation in the hands of users, they're allowed to block you for any number of weird reasons.
It sucks when server operators group together because it effectively becomes a centralized moderation team that makes decisions for users with tenuous implicit consent but user moderation lists aren't that.
https://github.com/matrix-org/matrix-doc/blob/msc2313/propos... is how it works fwiw.