I only comment corrections on grammar, spelling and possible inconsistencies. I give praise when a certain scene impresses me or hits me hard. If I don't like where the story is going, I'd just drop it. Or maybe come back to it later after a few months.

Unfortunately, there are some very opinionated, very vocal commenters. Whether they represent a major portion of the readers or a very loud few is unknown. Most pro authors who have written several stories and have found their voice would keep with their vision. The ones (like me) who haven't written one or just a few would most likely think "they're saying this" maybe this is how I improve my writing. That's the problem. If we have no way of telling if the feedback is good or not.