I was not talking about general comments bout about commenting on art done specifically for you. If someone spend hours doing something for you, you should at least say something in return, even if you dislike it so much you won't fave it. I would rather have a comment saying what is wrong with my art than thinking that the artist who it was meant for don't give a ... well, you know. And I'm not even talking about commissions but free art, like in an exchange. Free art is not so free. Some can spent an aweful lot of time doing the artwork. The last of feedback is like saying : I don't care if you spent a hole month on this, get lost!
This is the thing that hurt me more than anything else, because I don't have so much time and I would like to spend it for someone who cares.