I have down-voted an answer and left a comment asking the user to add more details to his answer. I always tend to leave a comment when I down-vote a question/answer to explain the reason of my action.
This happened many times and it started to be annoying. It's not about reputation, it's about down-voting an accepted correct answer without a reason. I also left a comment notifying the user that revenge isn't a good behavior, but I got no response from him.
I flagged the answer and explained to moderator asking for intervention. I got an answer after eight days and it was disappointing unfortunately.
All I'm asking is such users should be warned for behaving in a such way.