Personally I don't think downvoting just because you disagree is good etiquette. Especially if you are upvoting the other. I view a downvote warranted only when

Personally I don't think downvoting just because you disagree is good etiquette. Especially if you are upvoting the other. I view a downvote warranted only when a comment is rude, off-topic, or just unhelpful to the conversation (such "i agree" or "i disagree" with no other information provided). Everyone is entitled to have an opinion and just because you, or anyone else, doesn't agree with that opinion does not mean that their comment wasn't well thought and insightful. I have disagreed with people's comments, but their argument and presentation was excellent that I upvoted their comment.