What's misinformation? Things you don't think are true? Things the instance admin doesn't think are true? Things officially deemed untrue by the State? Or by the UN/WHO? Is is considered Misinformation if it was deemed Untrue in the past by State Officials but is now Official State Policy? We have always been at war with Eastasia. We have always recommended the wearing of masks. We have always seriously considered the possibility of a lab leak. Border closures are a bad, racist, problematic idea. No wait, now New Zealand is the hero of the pandemic because it closed its borders. We have always recommended border closures!
Servers defederating because of viagra/nigerian prince/etc. spam is one thing. A "lefty politics" server defederating with a "righty politics" server or vice-versa because they just want an echo chamber? Sure, you do you. General-purpose defederating other general-purpose servers because of "misinformation" and "trolling", when those terms basically mean "disagreeing with the current mainstream narrative on any controversial issue"? That's absurd. The generally-accepted issue with social media was for years that it created echo chambers. Now people are trying to use mastodon to create even more powerful echo chambers.
There seems to be an assumption in your writing that people should use social media to challenge themselves, be exposed to different views, to "discourse" and so on. Nearly everyone I know via social media wants to hang out with their friends, not debate people. Whether something is an echo chamber is sort of beside their goal, they want to have fun.
If one seeks out something that explicitly isn't an echo chamber, I'm sure there are many places for that. I'm just not seeing that as, really, at all desirable for a lot of people.
The problem is that Mastodon puts a second filter bubble on top of the old who-do-I-follow filter bubble. Except this additional filter bubble isn't controlled by yourself.
There is always a second filter bubble. In the case of non-federated sites, that filter is in the form of the policy of the site and also the algorithms used to sort feeds and replies.
They have a choice? Is it transparent for average users what is withheld from them and where? And where their own posts are withheld? If no, they don't really have a choice. If such a choice even exists.
Twitter is fairly lightly moderated I think, and the "following" tab gives a raw timeline.
Servers defederating because of viagra/nigerian prince/etc. spam is one thing. A "lefty politics" server defederating with a "righty politics" server or vice-versa because they just want an echo chamber? Sure, you do you. General-purpose defederating other general-purpose servers because of "misinformation" and "trolling", when those terms basically mean "disagreeing with the current mainstream narrative on any controversial issue"? That's absurd. The generally-accepted issue with social media was for years that it created echo chambers. Now people are trying to use mastodon to create even more powerful echo chambers.