my baby's in the white fluffy clouds

In my personal opinion, the ability to revise feedback isn't totally necessary. If a user deems it necessary to leave negative feedback, they had a negative experience, period. Just because they finally get their item or proof of shipment several months later doesn't make the experience they went through even neutral. Neutral means shipping was really slow without explanation, payments were delayed without reasonable cause, etc. When I am considering buying something from someone, if they have negative feedback that I view as legitimate, I personally skip the purchase regardless of whether or not the feedback was revised. I think many people feel the same because no one wants to fight a battle for what should be a simple transaction.