HN has a "Flame War" detector. When it detects a flame war it applies a penalty to the item in question, causing it to drop in the rankings.

The definition of "Flame War" is an interesting one:

* when an item gets to more than 40 comments,

* ... if there are more comments than votes,

* ... ... then it's likely to be a Flame War.

The idea is that HN wants things to be "Intellectually Interesting". TPTB seem to think that if something is interesting then it will get upvoted, and that seems reasonable.

OTOH, if there is a flame war then it's likely to be the same small group of people arguing back and forth. So the number of comments rises, but they can't repeatedly upvote, so the number of votes peaks early. Further, if it genuinely is a flame war then it's unlikely to get upvotes "from outside", and so there we have the conditions.

Occasionally it gets a false positive, so I saw somewhere that whenever the detector gets triggered, the item in question is reviewed by the mods. (Let me add here that the mods make decisions, and while some people will sometimes disagree, I think on the whole they do an amazing job. To them: Thank you.)

I suspect that this is a case in point: http://hnrankings.info/25870571/

I think it's a reasonable idea, the proxy of "more comments than points" seems defensible, and having the backstop of the mods checking things is reassuring. It's always disappointing when what I think is a reasonable discussion suddenly sinks without trace, but I believe HN is the better for it. It would be interesting to know how often it's triggered, and how many are then reversed.

[0] I'll try to add references when I can.