Each one of us may have our own criterion, as to when to up/downvote. I'm trying to see if some cases should be a common factor for all of us.
Imagine there's a question and some existing answers. You add another answer that is correct, and that it adds some key point, not yet mentioned in any pre-existing answer. That point is key in the sense that it even invalidates a big part of what the other answers were saying, at that time. Now, one of the other users sees your answer, agrees with your point, acknowledges with a comment, and corrects his answer. The correction is important both in number of edits, and in the concept behind it. My question is: taking into account that, if you hover over one answer's upvote arrow, it says "This answer is useful", shouldn't it be a common factor of all of our individual voting criteria that, in cases like this one, (at least) the person that used that important point should upvote that other answer? I think he should.
This happened to me yesterday, with this answer, which provided a key point, which was used to correct another answer, and it indeed was acknowledged with a comment, but I got no upvotes. Not that I care too much. I'm just curious to see how many people would also think we should acknowledge with a +1, in cases like this one.