The Value of Downvoting, or, How Hacker News Gets It Wrong

The reason HN doesn't need downvotes is that HN, unlike Reddit, kills lame articles. On Reddit, users need downvotes as a way of saying an article is lame. Downvoting is the only way you can get a (nonspam) submission off the frontpage. But on HN you can flag it and if it's bad the editors will kill it.

We can thus safely assume a nonlame set of articles, and we also (so far at least) assume nonlame voters. And if you only have nonlame voters voting on nonlame articles, upvotes should be enough to pick the winners.

I don't think Hacker News' system kills lame articles. I have seen obvious troll blog posts and such reach the top of HN repeatedly.

The reason this happens is because of the following. Let us say that an ordinary story that is completely relevant to Reddit and is worth reading is upvoted by 50 people and downvoted by 10. This gets the story +40. Now, let us take a very controversial story, say, a blog post on how much git sucks that is obviously fishing for links. This story gets upvoted by many more people, say, 100 people... and downvoted by 300. It doesn't get near the front page.

Now, take the same on HN. The first story gets +50, the second gets +100, despite the majority of people believing it should not be on the front page.

This is not to say that the Reddit system is better, but rather that the HN system is not perfect.