If a story came through our slush pile at PodCastle that had been vetted on this forum, and I loved it and wanted to buy it, then I would do so.
I won't be *participating* in the writer's forum here, so there wouldn't be any nepotism (I know that wasn't the concern that was brought up, but still). There's not even any particular reason why I'd know the story had been vetted in our private forum unless the writer mentioned it in their cover letter, but I'd recommend they not do so (in general it's not good etiquette to mention whether or where a story has been workshopped, and particularly how it was received in the workshop).