Will that stop the serial 'Why can't I vent and leave a negative?' sellers?

Doubtful.

Having said that, it might help the purveyors of auctions. So a possible viable improvement to the current system.

As I might have mentioned, I sell by BIN and NO buyer feedback/strike count/retraction count will assist me in vetting buyers. Blocking them on their invisible strike count does, though.

I have had 2 NPBs this week, which makes 4 in the last 18 months. That's life. I follow the processes and soldier on. And I suspect I'll sell both the relists in fairly short order. That's been the way of it, in my experience. The NPBs are on books that will sell anyway.