It's an interesting idea for sure, but I'm not sure how or if such a thing can exist. Moderation becomes a headache, and well, a lot of truly brilliant people I've met in life have zero interest in debating it. How do you keep out the YT commenters, Fox News or r/politics commenters, etc?
It would be interesting if HN had some bucket like /offtopic, for things that are flamebaity and removed from the main view, but I fear it would attract the aforementioned people who only ever troll there, and dang probably having zero interest in mod'ing it.
What if, along with the '/offtopic' bucket there were participation criteria that could be moderated by other /offtopic participants? Not my wheelhouse, but something like '/offtopic' threads are only readable by HN members, only editable by members in good standing, presence of an 'evict the troll' button that disallowed further comments on a thread if enough users press it about a given comment/user.
Such features will be abused by trolls, and that sooner than later. Case in point: Twitter's recent new policy about doxxing, that was instantly (as in, not even 24 hours after release) abused by a bunch of far-right mobs to silence BLM, antifa and feminist accounts.
Systems that ban people without a human (with decent training, context awareness and time to properly judge) in the loop should be straight out banned because of the abuse potential.