I don't appreciate the insinuation, I generally expect more from HN. But I'll bite.

I've only ever been banned once, myself. I used the words "January" and "6" in close proximity in a discussion, and it turns out it is an unwritten rule that you may not mention that date. I've had friends get banned because they posted in an unrelated subreddit that the moderators did not like. And I've seen randos banned for nothing more than observing that the moderators were reactionary. No attacking, no profanity or anything like that, just an observation and -bam-.

You can see hints of the frequency by the sheer number of "[deleted]" accounts that show up in a typical large discussion.

Reddit is a cesspool these days. Virtually all major subreddits are now dominated by politics, and you get banned quickly if you say something which is perceived to be against the preferred ideology of the moderator.