Slashdot also had upvotes with reasons, and I personally think that is just as important if you agree with downvotes with reasons: it lets you differentiate between things that added new information, made good arguments, or was simply funny.

That said, the problem with downvotes with reasons is that it now feels much more harsh. I'm downvoting something that is clearly an insulting comment that should not have been made on the site, and yet I'm wondering "do I really want to use the term 'troll'? that seems harsh".