I've been on the Internet since 1994, and it has always been the case that if you made a sufficiently odious pest of yourself over a long enough period of time, that someone would contact your university, employer or ISP, and you would lose your account, or at least your access to Usenet.

You were always perfectly free to go find a new account elsewhere if anyone would have you. But there was always a point where if you passed far enough beyond socially acceptable behavior, your Internet provider might choose to stop doing business with you.

This was especially true in the case of harassment, attacks on network infrastructure, and criminal behavior.

This is why *chan websites have gotten so popular. Being anonymous in everything you post is refreshing. Short of posting illegal content, almost anything goes.

"Refreshing" in the "great place to plan a coup" sense?

Eventually they are going to find that there's a limit to how much violence you can incite before getting slapped down, legally or otherwise.

No, anonymity is refreshing because a world where you are always on the record with your most formal identity with everything you say runs largely against the ways humans develop their worldviews: by trying on certain opinions, sorting themselves out, and participating in low stakes interactions where they can make mistakes and learn with minimal consequence.

This doesn't mean 'planning a coup' is one of these contexts, but you are focusing on a very narrow example of the broad social system impact of anonymity in online communication.

There's many reasons why I find it refreshing.

Other than anonymity, talking to people who have no incentive to karma-farm is very refreshing.

In websites like Reddit/HackerNews, the karma system gamifies posting. You "lose" if you post any wrongthink, and you "win" when you reiterate whatever is socially acceptable.

This means there are consequences to posting. In *chan websites, there is no consequence to posting your thoughts (or just trolling, because that's fun sometimes).

Are they popular ? They may be infamous, but I feel most of the brain matter has been evacuated from English-speaking boards a decade ago and they at best sustain their existing demographic.

Yes the "point where you passed far enough" is another way of saying there is contention, I'm not sure what your point is. If it was a zero or one state, there is no contention over it.