I wonder whether the bid bots could be countered by a captcha system of some kind. Incorporating it into the frontend sites is one thing, but coding for CLI and whatever other bot systems are in use is another. And then there's the problem of captchas being generally annoying to the real human users we want to encourage to curate. It's probably not a solution for abuse, but maybe thinking outside the box of tweaking reward percentages will spark someone to find a better solution at least.