Here's an idea when making constructive comments: suggest HOW to improve. Somebody may know something someone else does not. And if you don't know of any way, say so. But again, I have made helpful suggestions before and they were not too well received. I guess it depends on the personality type. Some want to learn, and some want a mindless slap on the back, not caring if their work ever improves. And some commentors' vocabulary doesn't extend past "OOOH", "WOW", "Gorgeous", etc. Eh - well, that's my two cents.

And don't call me Shirley!