I think the biggest difference between far-left and far-right communities is that far-left communities don't pretend to have free speech. And because they don't care about free speech they are more willing to shut down content that the host platform may object to, like calls to violence. See places like /r/latestagecapitalism.

The left understands the complexity of free speech, the right weaponizes free speech. Huge difference.

You cannot have both an open community on the internet and unmoderated content. The right says they do this, but it is a lie. Even cesspools like the chans have heavy moderation to keep them from turning into a porn distribution form.

/b/ is porn central. They do try to keep child porn off the site, but even that low bar is hard to achieve.

I don’t know about “communities”, but there were definitely many people calling for violence at BLM protests and marches in 2020.

The difference being that BLM movement actually has many decades (centuries?) of concrete evidence of racial injustice and oppression compared to the baseless claims of voter fraud and a supposed stolen election.

There are a lot of people that are unwilling to give an abused minority even the slightest leeway, and instead while holding the majority position holding power, claim they are the ones that are abused.