No, c242, that's not a comment, that's a personnal attack. Saying "That skin does nothing for me." is not an attack. I really don't think it's bad at all. I've seen far worse comments. The person is only saying that that style of skin isn't his thing.
Of course it wasn't too elaborate, but then again, tell me how "Great skin, man!" is in any way constructive and helpful? All it does is boast your ego, and I don't see anything constructive about that. Most people don't need a bigger ego.
I'm sorry, I'll be blunt: if you don't like negative comments, don't post your work in public. At this point, Davad, this isn't just for you, but for all the people who just want to be flattered about their work.
In short, long comments are better. But some people are lazy. Some people are incapable of typing more than 5 words in a row. The person who leaves as a comment "This skin sucks" on a skin he doesn't like is very likely to write "This skin rocks" about a skin he does like. Neither are helpful, either are meaningless. But if you accept the later, you have to accept the former as well, they are part of the same package.