When buyers go to enter negative feedback, they are given the opportunity to try to resolve the issue with the seller first.

If the above screen is ignored, buyers are then given a second opportunity to reconsider their decision, so it's not as if negative feedback can be left accidentally. Doing so is an intentional two-step process.

To be honest, that's good enough for me. If I bypass those two warnings, I'm absolutely certain I want to leave negative feedback.