For a truly open peer review I believe that all reviewers should be prepared to be public signatories and also be prepared to have their comments published alongside the document.
Even if the reviewer thinks the paper shouldn't be published this should be the case. If nothing else it might engender further interest and discussion if the topic.
It shows what a miserable state of affairs this business is in if a reviewer has to attack the author rather than argue the subject and is let get away with it. A reviewer like that should be blacklisted.