Are there other communities, online or off, with a similar balance between the quality of the original source material (whatever that means in context) and the responses to it? For example: an online forum dedicated to an esoteric interest; a book club or writing group; your local bicycle repair shop; etc.
(A lot of workplaces probably exhibit this balance, but let's leave them out of the definition of "communities" for the purposes of this post.)
https://www.reddit.com/r/AskHistorians has high quality researched answers but sometimes the first answer comes after hours or days so you need to bookmark the interesting threads.
Related "Ask HN: Alternatives to HN for non-Hacker News?" https://news.ycombinator.com/item?id=25318880
I've also noticed that other message boards usually become "productized" once it has a large enough audience, and that tends to drive down the quality of conversation as well. Since the HN forum is an offshoot of YC, that hasn't happened. Well, I guess HN could technically be considered a job board for YC companies, but those postings are dwarfed by the regular posts.
What seems to keep HN from going too far off the deep end is:
1: A clear, minimal set of guidelines that covers all bases
2: A mod who seems to have a good sense of where to enforce it and, I hope, gets paid to do it
3: A community that mostly seems to check itself
4: A custom forum that allows experimentation with system-level experiments in moderation and someone to develop those features
That being said, there are indeed many experts around here and I find it interesting to read their opinions (if they fall in their area of expertise :-)
I think most of us spend more time with comments than articles …
Variety of topics, highly competent answers, low noise