Ask HN: Do HN comment display rankings utilize exponential decay? | Hacker News Reader

Ask HN: Do HN comment display rankings utilize exponential decay?

3 pointsjqueryin3 comments

I'm asking this question because I've noticed over the years that (in my case) it's been extremely beneficial to be an early commenter on trending posts. This isn't to say you can or should post meaningless comments, but early contributive comments seem to fair far better than late contributions. My initial inclination is that comments do not appear to utilize a decay algorithm to the effect that stories do. If this isn't the case, it would appear as though I have spurts of insightfulness on rare occasions.

I'd imagine it's just because earlier comments have more time to gain points than later ones, and as a comment gains points it also gains visibility, which kind of snowballs.

If you think about it, it wouldn't really make sense to have comment rankings decay. Breaking news is only breaking news for so long, so it works for the front page, but a valid, insightful comment on a particular story doesn't lose value over time.

Side note... I might be wrong, but I think the stories use a rational decay (current point value divided by time since post) and not an exponential one.

You can see comment order reshuffling in the seeming absence of votes so you can be pretty sure there's not exponential decay, which would preserve order.

The simplificated formula is:

  x = (points)/(time_in_hours)^1.4

but the actual formula has a lot of secret sauce.

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