This is a bug report, not a feature request, but I couldn't find an obvious place to put it. I appear to be able to upvote comments an infinite number of times: if I click the upvote button once, it disappears. But if I hit enter, the vote keeps climbing. I have some screenshots of this in action.
Unless Hacker News has an (undocumented?) feature that lets regular posters / certain karma thresholds / whatever have a large or infinite number of votes, this appears to be a bug.
I'm running Firefox 3.6.8 on OS 10.6.whatever is latest.