The point of a no-comment policy, while ostensibly intended to protect the former employer, can also be a way for a reference to avoid revealing negative job performance information which the reference knows to be true. “I liked Charlie. He was a good guy, but I can’t really say much more than that about him because of company policy.” Should that sort of comment be a red flag – if Charlie asked that person to be a reference for him and the person agreed? Yes, absolutely!
How do you deal with an equivocal comment like that if you’re the prospective employer? Well, for one thing, this is why you check more than one reference. If the candidate provided three otherwise appropriate references – whom he asked to serve as his references and which they agreed to do – and all three still hide behind company policy, I would be concerned not only about Charlie’s judgment, but also, and more importantly, about Charlie’s suitability for the position. If this ever happens to you and it will occasionally, I would look for another candidate!