What was the best feedback you've received on a piece of writing?

Well I had my teacher said wow (she thought I was dumb pfft) and she also said you have excellent ideas and really flesh out your stories

The best feedback I've ever received on a piece of writing was not the kindest. So I'm not sure what you're asking exactly. Although, you seem to be equating nicest comment with best feedback. So I'll try and share both.

I believe the nicest encouragement I got was in the third grade, when I wrote a poem about pussy willows. My teacher was so impressed, she used my poem as a model and I was so proud of myself. It's one of the things that got me into writing.

The best feedback I've ever gotten was from my short story class just two months ago. We had a writer's group discussion about one of our works every class, and mine was up. Everyone had such insightful comments and criticisms and I took copious notes. I got five suggestions for alternate endings, most of which I never even considered and were ten times better than what I'd written. They noticed things I neglected, told me what I needed to clarify, and inquired about character attributes, and "Would Jill really do that in that situation?"

I've had a lot of writer's group sessions like that, but this one was by far the most valuable, and I really appreciated everyone's input.

I guess the moral of this experience is, the earlier you are in your writing career, the nicer the praise. The more you go down that path, the more valuable the critiques. And remember, critique does not mean "criticism," it means a well-rounded analysis.