creative people want (if they're serious about being good at what they create) to hear critical feedback more than they want to hear 20 variations of "i liked it."
"I'd have reworded paragraph 2 to be more clear" or "you need to rework this section to read more smoothly" are both fine, and are not negative comments.
"That's the biggest pile of stinking dog crap I've ever read" would be somewhat negative and might be frowned upon
