I agree, when you have paid you have done your share of the deal and feedback should be left. It is clearly so they can leave bad feedback if you do in the hope that you will agree to remove it. I bought a CV joint, 4 weeks later it had not arrived. I had spent two weeks trying to get a hold of the seller. In the end I left bad feedback: "Over a month and no CV Joint. No answer to emails, phone or Skype calls. Avoid!" And I got the following put as negative feedback against me: "Way to hasty to leave negative feedback. Watch out for him." So the seller was saying that hearing nothing for four weeks is hasty! And this is for a car part! Surprise, surprise a few days later he asks to mutually withdraw the feedback! Which out of principle I refused to do. It is not me that people need to watch out for.