How is this at the top of HN? Apparently people that need this stuff sit on HN and vote it up. If you don't want to go to these sites I have some advice: Don't go to them.
Once you start commenting online, you can't easily stop. So it's not as simple as "Don't go to them".
</recovering addicts view>
That means it's a game.
"winning" games is fun.
Thus increasing your karma score is, well, fun.
Not to mention all the fringe benefits a decent karma score can bring you ... well not really the karma score itself, but the activities you do to get said score. It's really just putting "How useful you are to the community" into a cold hard integer.
Being useful/known/etc. in the right communities has been a pretty damn important thing since forever.
As always, what matters is what you do with all of this. Just having it by itself doesn't mean a thing.
If tools like this can help, then that can be nothing but a good thing, I don't think there is any need to be derisive about it.