When I talked through the game theory of BlueSky with the founder, it seemed that it would tend more towards competition between a few large services with fairl

When I talked through the game theory of BlueSky with the founder, it seemed that it would tend more towards competition between a few large services with fairly nuanced and predictable moderation policies. It is very easy to move your account and your followers to a new server, so if a big server started operating in the way you describe a large exodus would happen fairly quickly. But you have to make sure you are on a server that isn't being blocked by the other large servers, e.g. Donald Trump's server, some spammer's server, or a server that is difficult to distinguish from a spammer (like your own small server) so there will be an incentive for popular accounts that value their reach to stay on big servers shared by many other popular accounts that are hard to block without users noticing. So, the situation isn't so bleak as you describe, but also, yeah, controlling the website or app called "Bluesky" is still a moat (until it's not!)