Of course if nobody ever commented then none of us would ever learn anything. Personally I can usually tell the difference between honest, constructive criticism and somebody trying to be unpleasant, and I just ignore the latter. There are some comments which are difficult to classify like this, either because the commenter's native language isn't English or because they have an unfortunate way of expressing things, but that's life.

Those comments intended to be helpful, though, are worth a great deal, because they represent genuine criticism from which I can learn. Comments from friends or family are useless because they will presumably try to be supportive even if they think your images are dreadful.

For me, I know my images aren't very good, so I want people to comment and if they do say something constructive I can either listen and learn or ignore if I don't agree. The genuine trolls bother me not at all. But I do agree with one point - if artists don't like the comments they get, why let others make comments? It's just a tick box, after all, to remove that possibility (but then they wouldn't get the 'wow, awesome' comments that I guess they like).

Steve