Personnally, I do not have any time to comment (wish I did). However, when I read my own comments, I always prefer to get comments which tell me about something I can improve on. I don't even mind a comment like 'that is a lousy image', becuase I'd rather know that something sucks and get rid of it (since I know what I don't like about each of my images, and on most there's quite a lot, I am not offended, it just means that someone saw all the things I did and thought them important).