HN is the most moderated platform I currently use, but despite its rules and frequent mod intervention, it seems to have a higher overall quality of discussion compared to what I can find on Reddit or Twitter.
Discussion is of high quality as long as it remains aligned, which is true 99% of the time.
I would re-characterize it as "some Reddit subreddits are far worse" - because your experience can vary widely. All the subreddits I subscribe to (hobby and interest related, not news/politics) are actually self-policed very well. I tend to think the toxic subreddits are actually in the minority even though they get all the attention.
I find Reddit to be pretty good in general. All the subreddits I subscribe to (none are political or hot topics, they're all around my hobbies and interests, etc) are pretty civil. I am sure there are toxic subreddits, but my Reddit feed is higher quality than my Facebook feed by a mile, and the discussions might have a few corny jokes, but they're generally fine.