If this is the only thing you are debating, I’ll give a thought experiment.
I spool up a public Mastadon instance. I pay for the server, or we could even say I self host on hardware I own. Users join the instance, and I run a scheduled algorithm that bans 1 user per year with no recourse. Every 5 years I run a job that bans a random moderator.
Is it fair? Absolutely not, it’s a dumb thing to do. But who’s going to stop me? What law have I violated? I don’t answer to a board of trustees, investors, or anyone but the government. And the government says yeah it’s your server, or they say it’s against the law and fine me.
Or a more nuanced thought experiment: let’s say I’m the perfect admin and have upheld feee speech to the highest capability that I’m able to. I lose my job, run out of cash, and without warning the server running the instance dies, and I was irresponsible and took no backups - lost forever. I have now unintentionally censored everyone on my platform. Other than ask me to get it up and running again, or hand money my way, what is a user expected to do without the admin to get the same platform up and running again?
Google has sunset many of their services, and there is some page that has some list of everything they’ve killed. I’ve been on forums where the server admin said “yup I can’t keep the lights on, good luck and god speed”. I’ve also attempted to log onto an older forums to see a 404 and all of my prior peers lost to time. These aren’t unique problems to Mastadon, it’s the inherit problem of software running on someone’s else’s computer.
This is mostly my opinion as well.
The only tangible difference is that there is an option to switch instances and still be a part of the community, and laterally shift trust in server admins on the same platform. Centralized servers you get only one admin to trust. One to one vs one to many of platform to admins to trust. But the amount of drama from this is just multiplied and seems annoying to deal with as a user.
Still, the echo chambers will naturally form on all social media. Algorithms put you in your place, Mastadon administrators decide who you get to talk to. These suck because the power is not in the user to decide who they do and don’t see, whether explicitly by banning or implicitly through algorithms. The analogy of the house here weakens because these are public forums with multiple levels of power structure. It’s more like a Home Owners Association saying which other HOAs you can talk to, which is as stupid as it sounds. (Analogy breaks down as I think you can still read what other instances are up to, so no censored from a read-only standpoint jsut two way comms?). Analogies for federation are just weak, so I give up lol.
But if users have the freedom to choose who they do and don’t see via blocking by their choice, then at least the echo chamber is of their own design and not the powers that be. This is likely what you and I are both trying to get to agree on?
But there will always exist some person in charge of the server that decides what stays and goes by their sole decision alone, even if it was an isolated single instance, as they are the ones who have the SSH keys to the house and admin rights. Only way around this is to be an admin yourself and own your own home. With self hosting this is possible. With centralized services, not possible.