Ah, see, I see a marked difference between pointing out typos or a missed html tag and structure, theme, plot, canon-compliance, etc. criticism of a story.

One is telling the person washing the windows that they missed a spot--and they may or may not care. The other is telling them they need to rethink the kind of cleaner they use, how they wash the window, what sort of squeegee they have and the correct placement of the stepladder--and that could get you a bucket of water dumped on your head.

I would want to design any hypothetical feedback system for this sort of thing to allow people to separate those two concepts in terms of what they request or discourage people to provide.