It's kind of old now, 5 hrs with 30 up votes is sort of stale and it has more comments than up votes so probably got dinged by flame war detector too.

If something is controversial and doesn't have very many upvotes, its rank takes a nosedive once it reaches 40 comments.

As others have said, there is a heuristic flame war detector. It seems that a penalty is applied if an item has more than 40 comments, and fewer points than comments. It's actually a good idea, but it has many false positives.

That said, if people want to comment on something but don't think it's worth upvoting, maybe it really doesn't belong on the front page.

Thanks, learned something new :)