In my defense:
1) There's definitely an element of "if the user can’t find it, the feature doesn't exist" with downvoting here.
2) In practical terms, downvotes are so extraordinarily rare on HN that they almost don’t exist.
Anyway, I'm encouraged that downvotes exist on HN, but the threshold could be considered so absurdly high that they're nerfed into oblivion.
See:
http://news.ycombinator.com/item?id=507278
http://news.ycombinator.com/item?id=507604 (the downvoting on this does seem questionable, although it is an extreme position)
(Edit to add: I should mention I'm not talking about foul-mouthed racial slurs getting tolerated out of a total desire to let it all hang out. Its more that views which are quite possibly locally unpopular get tolerated, particularly when not obviously trolling. "Rails docs suxorz" would probably end up gray. "The quality of documentation in Rails is subpar, and has been for years. The platform changes so fast that significant features of the most recent releases are documented only on blog posts, if that. The wiki is an unusable mess, bordering on unreadable and filled with information which is out of date or merely wrong." would almost certainly not end up gray, despite the fact that Rails is very popular with the crowd who hangs out here.)
Another reason is that while the signal to noise ratio is not quite infinite the signal to "#$%!"# ratio is pretty close to it. I have omitted the word I wanted to use almost entirely out of my concern that it would be inappropriate for HN. That says something right there. To see it, click here:
http://www.penny-arcade.com/comic/2004/03/19/
The following are taken directly from another popular news site, at random from the #1 story today.
[Ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha ha. That was rich.]
[It'll be as big as that book of his, that totally revolutionized science! Oh, wait, nevermind.]
[The next Cuil!]
These three comments were heavily encouraged by the community on the other news site. They would not be encouraged here. This tends to prevent other people from seeing "Aha, sarcastic one-liners are what is valued, I should probably work on my sarcastic one-liners" and drowning most of the value-adding discussion.
And they don't exist for article submissions, which is problematic for all the same reasons I listed in the blog entry.
2) That's largely because few users make comments lame enough to be downvoted. But when they do, they get downvoted: http://news.ycombinator.com/item?id=507604
that suggests they are overutilized elsewhere and work pretty well here, I am not adverse to opposing viewpoints, I just dont want to see plainly dumb comments, if you overuse it, then it loses meaning.
(taking this thread as a test data, while I dont agree with a lot of what people have said, I wouldnt have downvoted any)
There aren't article downvotes-- but there doesn't seem to be a need for them. The moderators kill stories that are plainly inappropriate, and the ranking algorithm makes it difficult for things to reach the front page without a decent number of upvotes in a short period of time.
My point is: this is an interesting and subtle topic, and it might be in your best interest to study it in some detail, rather than just glancing superficially at what others are doing and forming conclusions thereupon.
It sounds like you didn't actually understand the dynamics of the HN community. You sound silly insisting your initial impression is even partially right, when the whole community is telling you the opposite. (This applies only to posts, of course. Downvotes still don't exist for stories themselves, outside of flagging.)
As for your assertion that not disclosing the karma threshold for downvoting is 'bizarre', I'd argue it's useful not to provide an exact number. Enough video games have 'achievements' listed out for people to obtain... I'd rather have people participate honestly than just to gain more 'abilities'.
It's not because you don't see them directly a lot that they don't have an impact. A comment that ends at +3 with 7 upvotes and 3 downvotes would have ended at +7 (or more because of the "momentum effect") if there weren't downvotes.