I think it's ok to use the up and down arrows to express agreement. Obviously the uparrows aren't only for applauding politeness, so it seems reasonable that the downarrows aren't only for booing rudeness.
It only becomes abuse when people resort to karma bombing: downvoting a lot of comments by one user without reading them in order to subtract maximum karma. Fortunately we now have several levels of software to protect against that.
http://news.ycombinator.com/item?id=117171
I think it's ok to use the up and down arrows to express agreement. Obviously the uparrows aren't only for applauding politeness, so it seems reasonable that the downarrows aren't only for booing rudeness.
It only becomes abuse when people resort to karma bombing: downvoting a lot of comments by one user without reading them in order to subtract maximum karma. Fortunately we now have several levels of software to protect against that.