If you'll look at the bottom right of my post here, and yours, you'll notice a green + and a red - sign. While I'm sure some folks just go clicking through because they've got nothing better to do, it does seem to be a decent indicator of one's use. I don't read into it a whole lot, but I'm hanging at a steady 'neutral' rating of 0, so it can't be that far off.
Post one terrible comment in a high-traffic thread, and surely it will go down a tad, regardless of how good you are the rest of the time. I've never bothered to use the function myself, but a few here definitely earned their reputations.