I personally don't use the downvote button unless on a serious case like a clear case of plagiarism or when I stumble on phishing link. One thing I dislike about downvoting, is people using it to count scores i.e some form of attack on people they don't like.
About downvoting because you feel the post is over rewarded, that is a subjective matter, as we don't usually all like the same thing. Been in a decentralized system I believe people are free to post whatever they like as long it's original and it resonates with their audience