They are less echo-chambery than Lemmy.world, in my opinion, as Lemmy.world largely aligns with the status quo and as such cutting out communists means you aren't exposed to communist perspectives at all, while on Hexbear, which is less broadly federated than Lemmy.ml, you still can't avoid engaging with liberalism when off of Hexbear.

In other words, Hexbear is a place carved out for communists by communists, but Hexbear users can't actually avoid interacting with liberals. Lemmy.world, on the other hand, aligns with the status quo, and cuts out viewpoints that go against that, meaning they can avoid engaging with communists to a far greater degree.

They aren't, no.

"no guys it's totally not an echo chamber, we just ban and/or relentlessly attempt to troll anyone with a differing opinion than ours!"

I'd say it's an impressive level of cognitive dissonance, but then, you'd already have to have that to believe China is a socialist utopia. Really it's just Tuesday for them.