"software which demotes overheated discussions" is pretty noticeable. It seems as soon as a story gets more comments than it has points, it drops like a rock from the front page.
IMO this is by far one of the best features of HN - discussion quality tends to nosedive on such threads, or more accurately, be buried under unrelated (frequently political, emotionally-charged, and/or low-effort) comments.
> "How are stories ranked?"
> "The basic algorithm divides points by a power of the time since a story was submitted. Comments in threads are ranked the same way."
> "Other factors affecting rank include user flags, anti-abuse software, software which demotes overheated discussions, and moderator intervention."