Don’t know about algorithms, but HN does a good job of being a forum. I think it’s a combination of sensible guidelines, restricted community moderation (votes and flags) and very good manual moderation.
I never thought much about it before, but I guess forums should optimize the useful life of a given thread to loosely match the useful life of whatever is being discussed. For example, golfmk7.com is for a set of cars with model years of 2015-2021 (in the US; 2012-2021 globally) so the critical mass of discussions will probably taper off in the next 5-10 years.
I don't know the typical lifecycle of homebrew equipment, but a similar bell curve distribution should apply.
Very different timeline from discussing news and/or random gossip where nobody will care about that particular conversation a week later.
