I find building out forums exceedingly fun too (which is why I've been at it for a decade). Like you, we realized that federation between forums is quite important from a communication POV, though I'm not sure if you went that direction or just used PDSes as your user store.
We ended up integrating ActivityPub and its really reinvigorated my passion for building forums again :)
Usually when someone on HN talks about building a forum out, I tell them it took me a year (3 devs) before we reached rough feature parity. Perhaps it's possible for AI assisted clones to reach this point in weeks or months rather than years.
Good luck! When you get tired of it, just tell your agent to migrate all your data to NodeBB.
I just had a fun thought. Rather than permanently collapsing a comment when it reached some level of undesirable it can be a % of the time where the % increases with activity and the number of replies. Even if you can detect great comments they normally drown out other candidates. If the topic is active enough unfolding those 30% of the time is enough visibility.
Try make it more like objective a-b testing where things are compared on a level playing field.
New posts should sort to the top in a sub forum but (like hn) it isn't required to only have new posts there, highly rated slightly older things may mix in but (to a lesser degree) older and less popular topics can also be mixed in. If no one looked at it we don't know if it is any good, it might be just what the project needed.
If the judgement isn't as final ai can also assist with ratings.