Not likely. Consider an extreme example where they admit they didn't hire you because you are black. They broke the law and cannot be protected.

In other words, your signature does not provide a lot of legal security

Because the default tends to be to say nothing, frequently if you just ask directly for feedback may get it. Its a bit of a back door to the policy.

When I worked for "MegaCorp" we didn't give any feedback voluntarily but if a candidate asked me directly I would let them know. I frequently hired junior engineers* and felt almost a responsibility to give them some input, particularly if their issue was technical. If they were just an ass, I'd likely stick to the company line and not say anything.

* I found most senior engineers are pretty well aware of their deficiencies and almost never would ask for feedback.

> Is there a way I can just waive my ability to sue? I would love to know my weaknesses in the eyes of others.

If you could (and it was binding), HR departments would try to require such waivers.