Currently, the downvote button's tooltip says
This answer is not useful
That's how it looks like:
Consider a question with 5 answers, of which only one happened to be useful for me. Obeying the downvote button's tooltip, I'd downvote all of the other answers...
I suggest rewording that tooltip, to something like:
This answer is wrong or misleading
This should give more focus as to what are we downvoting for (mankind as opposed to myself :-) ).
Since this comes a bit hard here, I'll elaborate some more:
There are actually not so much reasons for which we should downvote:
- Unclarity isn't reason enough for downvote. It should be commented or edited. We've got the power to do that.
- A comment-answer is a usage problem and should be treated otherwise: directing the responder to the the answers guide.
- Dead link answer should be commented as to give a chance for fixing it.
What are you left with? Wrong or misleading.
What do I propose? Exactly that.
Furthermore, users that read an answer as a possible solution for their own problem, don't need downvotes in order to understand that a broken link, an unclear answer or a comment-answer are non-useful.
Where do they need downvote most? In the wrong and misleading answers. There's no other tool for them to distinguish the good from the bad.