I think the main problem with having your work criticized here, is that this critiques are usually made right in the gallery, right under your beloved pic, so that any passer by will see the picture, then read the critique just after and they will think "this needs a lot of improvement" whereas they would perhaps have thought "wow ! Great !". When I think I can say something to improve on an image, I don't post this advice in the gallery : I give positive advice in the gallery (outlining what I like), and then send a personal IM to the author about what I thought could be improved. I found that it bruised less toes, and no one complained or call me a troll (even people who did not agree with my opinion). Just my 2 eurocents.