>If discord had a bit more work that would enable persistent threads like reddit, and encouraged longer, more thoughtful posts like HN and quality moderation, it would be perfect.

Facebook Groups is this product - but it's exceedingly difficult to find the small percentage of well-moderated, smaller groups which are specialized/for enthusiasts. Also, the FB sub-comment/response structure is far worse than HN or Reddit and leaves much to be desired. But I've joined a few with good moderation and thoughtful, interesting discussions.

That being said, any group with [thousands] of members or loose moderation devolves into an absolute shitshow of shit posting and scam/spam posters.