It would be fine with me if there were such a board for that. But you shouldn't worry too much about a bad review once in a while. If you have mostly stellar reviews and get a very bad review I personaly usualy assume that it was just a problem between you and this particular client. And if it is very bad then I tend to believe that you and the client had some personal difficulties and he got pissed and wrote the review. So I don't give that type of review much levity. But I do understand the need to defend yourself and your reputation.