I had this limitation on my account for a while too. It was because I was upvoting flame-bait comments that had been grayed out. My personal reasoning at the ti

I had this limitation on my account for a while too. It was because I was upvoting flame-bait comments that had been grayed out. My personal reasoning at the time was "but the other poster started it" (these were deeply nested angry comment chains). After a couple of months I emailed dang to request if I could get real voting back and he took the penalty off my account, after explaining why it had been put there in the first place. If you see an ugly exchange of comments, DO downvote (or ignore) provocations. DON'T upvote provocative retorts, even if you think that the reaction was justified. And if you get your account penalized, you can have the penalties lifted with an email to hn@ycombinator.com.