What garfield said.

I don't have the opportunity to vet buyers before a sale as almost all my listings are BIN, so negative feedback (or negative positives) are of no use to me. Even with auctions, most bids are placed in the last few seconds so, once again, no chance to vet bidders.

Leaving the NPB a strike does benefit me. Like all prudent sellers I have my blocks set for bidders with 2 or more strikes. They can't buy from me, I don't need to check their feedback.

If all sellers did this, then the serial offenders wouldn't be able to buy at all, and there would be no problem.

If you successfully closed a NPB case, you shouldn't be able to leave ANY feedback, as no transaction occurred.