Online communities that allow upvoting / downvoting have been effectively dead for a long time because it's easy to manipulate conversations by elevating and punishing comments to fit a narrative. This is especially true on HN.
On the other hand I think you need reputation mechanism. The biggest problem of online communities is that every moron (or a bot) has equal voice. Clearly democratic upvotes/downvotes don't work very well though. Someone who solves it is going to be the next billionaire.
Ironically, aggregator communities like reddit came about because forum communities were dying off. Memeing about the latest news injected "life" (if you want to call it that) into the internet. AI is just taking out the trash, in my eyes.