One of my pet peeves is when people downvote a post and you you have no idea why I think a good change t the system would be if you do wish to downvote a post you must also leave a comment, although some may leave a generic message which still would not help one to understand why your post was selected for a downvote but perhaps n a lot of cases you would get some sort of explanation

if i ever give a downvote then I also leave a comment saying why