It's not a horrible idea... the challenge there would be making that payment/refund flow totally transparent in order to build trust and be fair to the researchers.
First question: Do you keep money for shit reports?
Well no, you have to pay it back like credit card validation. There is no pain for posting shit report just inconvenience. There is no legal way where you can keep the money.
I am not an accountant so ask some accountants why not.
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