Truth!
...Oh, right, no one-liners. ^_^
Adarias, you brought up a pet peeve of mine, that of people posting art and screaming "ZOMG THIS SUCKS!" If you as the artist insist it's so awful, why should anyone else think differently? More to the point, why should anyone else put their time and effort into giving any critique, if you yourself can't even take any sort of pride in your work? As you've said, humility is one thing, and self-deprecation can be charming, but don't push it too far.
I agree that ass-patting can be nice for the artist, but as Helm has pointed out, the more one-line ass-patting that goes down, the more difficult it is to sift through and find solid critique (I've seen this happen a lot on CGTalk, among other places).
Here's another pet peeve, while we're at it. "Check this out, I spent like 5 minutes on it!"
And I will spend exactly 0.5 seconds skipping that thread.
am_pm: Also good points. Complete overhauls sometimes have their place, but those comments should, nay, must, be backed up with some solid direction, whether an edit, good explanations and reasoning, etc. That way the OP can at least make relatively sound judgment.