>>8,9
Regarding Twitter, I recommend reading White by Bret Easton Ellis. He's a left-leaning gay writer (I never knew he was gay, he doesn't seem to make a whole identity from his sexual orientation). You'll learn more about ``Generation Wuss'' and harassment from the other side of the political spectrum. It's probably one of the best essay I've read in 2019 (I troll you not) and it's a story of contemporary events (post-2016 global nervous breakdown)
Otherwise, I agree with you on Mastodon. The signal/noise ratio is immeasurably better than Twitter's. It simply doesn't appeal to nazi trolls. Discussions seem to be more technical than political anyway and the alt-right simpletons have their own Gab Twitter clone. I don't miss the emotional crew either, to be honest. Besides, Mastodon's interface is not only user-friendly: it's beautiful. It's a proof that open source projects can come with polished UIs too.
>>11,12
Federated networks have that inherent problem: some content could be censored on a particular instance but not on another. If your interests are programming, technology and knitting, and if you're careful to stay away from the political shitshow, I doubt you'll notice it anyway.