Another eBay feedback improver
Earlier, I wrote some proposals for improving ebay style feedback, including not having feedback revealed until both have left it. That has some flaws, but the main reason eBay is unlikely to do this is that eBay likes feedback to be positive, they want to convince buyers it is safe to shop there.
So here's an alternate idea to prevent revenge feedback. Revenge feedback is only vaguely in eBay's interests, in that the fear of it keeps feedback positive, but the existence of it adds to the negatives.
To solve this, attempt to detect revenge feedback and print statistics on it. What would be detected is negative feedback left by a seller on a buyer after the buyer has left negative feedback, but not if the buyer left this feedback immediately.
In theory the buyer has just one duty -- to pay promptly. Indeed, since eBay owns PayPal they could also just report about buyers whether they paid promptly with PP and that should be all you need to know. Sellers might want to tag a "troublesome buyer" who has a lot of complaints after getting the item but I think that's in an entirely different class of feedback anyway.
So really, a seller should leave feedback once the buyer has paid, and negative feedback only if the buyer pays slowly, pays falsely or doesn't contact the seller.
Under my system above, if the seller waits to give feedback, in particular waits until after the buyer gives feedback, she's taking a risk that her own negative feedback will get counted in the revenge count. And a high revenge count will scare away deals, deservedly.
More simply, the system could also just count how often the feedback came in the expected order (Seller's first, then Buyer's) and how often the other way around. This would strongly encourage sellers to feedback first. You would see when bidding that a seller always or rarely feedbacks on payment, and again, stay away from those who don't.
Now admittedly, with the fear of revenge feedback gone, buyers would be more honest, and reputations would drop a bit. eBay might still want to avoid this, but with luck it would not be a big change.
Updated thoughts: It may be time for a 3rd party company to begin offering more detailed reputation information. Since eBay has stopped robots it doesn't like, this would have to be on-client software which extracts results of transactions from eBay to another database that a browser add-on (like ShortShip) can display. All the useful information could be stored -- feedback order, possible revenges, feedback based on dollar volume etc. Counting no-feedback transactions is harder and probably requires a blockable spidering operation or some complex shared network. To this one could add more feedback done outside of ebay, including revenge claims and full text stories that eBay doesn't allow in feedback comments.
Useful hint: eBay doesn't allow URLs in feedback, but if you invent a random string you can put 'Search for randomstring' in the feedback comment, and make a web page with that string in it that Google and the rest will find. Then people wanting to know more than 80 characters can learn it. Of course, the other party can also make a web page with that string so searchers see both sides, which is fine. A good non-random string might be something like eBay followed by the item number, as in 'eBay130064299000' -- in fact, if such a method became common you could search for it without even needing it in the feedback.