At the risk of being somewhat off-topic (there really should be a "tools other communities use" page but as far as I can see it does not exist yet), someone recently wrote up the discussion/moderation features of Hacker News, which IMO make an interesting read.
Topic on Talk:Talk pages consultation 2019/Tools in use
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@TBolliger (WMF) and @SPoore (WMF) might be interested in some of those. I believe that the ability to collapse sections of very long discussions has been mentioned by a Wikipedia editor, although I can't remember where offhand.