I think the posts on HN are often good, and it's typical to find at least a couple insightful or informed top-level comments about them. But after that, replies to those comments, and then the replies to those replies, typically don't add much value. I have my theories about why that happens, but in any case I doubt the site would benefit from leaning in to one of its weaker aspects.

I think you might respond that improving the site's discussion features would improve the quality of the discussion. But I am skeptical that would happen: it feels like an engineering approach rather than a community approach. The best discussion sites on the internet have worked consistently because of the crowd they attract, and the pressure moderators apply, not because they had a certain feature set.