the torrent analogy is pretty good actually, ISPs can block certain connections so a good chunk of users miss out on the swarm, and the swarm misses out on them. where federation differs from choosing an ISP is it's far easier to switch your provider to this service than it is an ISP.

and where a given instance draws the line on censorship isn't the be all and end all of whether other instances federate with them. as i see it, though my understanding of this comes from mastodon, even if one server decides to properly block another, a third server might chose to limit instead, if at all. there are block lists but that requires a very obvious and widely shared red line on freedom of expression, where there are very few places on the open web where you'll see less censorship than that.

in the end, wherever a given instance draws the line, is far more democratic than other social media sites. it's easier to think that twitter, or reddit, or facebook, is more accountable, because there's at least one guy everybody can point to to blame when something goes wrong, and sure, there'd be something in that, if the scrutiny they get actually changed anything.