On the contrary, after accumulating a certain amount of karma (500 points??) a user gains the ability to downvote comments (but not stories).

Also, downvoting is only available for a certain comment age. Once the comment is X hours old, you lose the ability to downvote, but can still upvote.

X should be 24 hours https://github.com/wting/hackernews/blob/master/news.arc#L10...

thanks for the neg reps, really shows your attitude towards newcomers