Your contention is patently false that a NO review or mentioning negatives will damage your ability to see providers in any way. Phrased in an objective and diplomatic way anyone can say anything at all. If you handle yourself with class and do not come across as having an agenda no one will fault you for sharing your experience.
Where guys run into trouble is in stooping to being inflammatory, insulting, or uncouth not just in the review itself but in any follow up conversations that may occur. If the lady posts a rebuttal thread in Coed it often backfires on someone, I do agree. But my assertion is that it backfires on the one who comes across as full of shit or trying to spin it in some way, not the guy necessarily. The problem is that many guys come on here and just act like absolute assholes so they get no credibility with the ladies and may indeed wind up on various DNS lists, and for good reason.
Anyone who thinks they can't write negative things in a review without repercussions is just ignorant. I've written several NO reviews, each one of them deserved. Even in my Yes reviews I try to objectively detail both the positives AND the negative/less than ideal things that happened or that I observed. I've never had a single problem as a result. Why? Because I'm not an asshole, I don't say things in my review that I wouldn't say in public if it came down to it, and I have no axe to grind nor agenda other than sharing information...the entire point of this site.
Personally I find it hard to take it seriously when I read a total puff piece review that contains nothing even remotely negative in it at all. No experience is 100% ideal, so I know they are leaving things out I just don't know what. Same goes for reviews that are so hostile and emotionally charged that it seems obvious the person is not being objective. Both of those types of reviews are of limited usefulness in my mind.