One of the most pernicious parts of Twitter is how people will retweet
something dumb, offensive, or awful that an opponent said, along with
a message mocking that opponent. Over time, this leads people on all
sides of an issue to see only a distorted caricature of their
opponents, comprised of an amalgam of all the worst features of that
group. (This phenomenon of cherry-picking the worst bits of an
opposing group exists independently of Twitter, but Twitter makes it
much, much worse.)
How does Mastodon solve this issue? Well, Mastodon doesn't have
retweets; it has "boosts". Boosts are essentially like retweets, with
one key difference: there's no option to add your own commentary. You
simply can't post something awful with a message saying how awful it
is... [On Mastadon, if you boost] something you disagree with, you're
ultimately giving that viewpoint more exposure, not less.