I don't see how it's possible to abuse the rating system as a seller. If the buyer pays you right away, positive. If the buyer lags but eventually pays, neutral. If the buyer flakes out and doesn't pay, negative.
I think the feedback system is more open to abuse with buyers. Sometimes people buy something and they have unrealistic expectations or they have buyers remorse and want to get a refund after playing with the item for a few days. So far as a seller I've had mostly good luck, but I've experienced a few incidents where you ask yourself..... "Seriously??"
Agreed with all of this. What I do to protect myself is that I take pictures of each item, with time/date stamp turned on. I've only had to fall back on the pics once. I had one guy try to pull that "It was damaged when it arrived and I want an instant refund"....two weeks after he'd taken arrival of the package (had the tracking number history to show concrete proof). He opened a Paypal dispute, which I updated with the pics, and asked "If it was damaged, why did it take you two weeks to let me know? Also, as you can see, the item was perfect when I shipped it out". Instead of replying, the guy actually closed the case, and I never heard from him again, and I blocked him from my auctions from that point forward. Dude had probably tried that trick with other sellers in the past, but I don't play that game. Ebay are dreadful, but Paypal at least gives the seller a chance to prove their side of things, and won't instantly vote in the buyer's favor.