Sure, the very same day such feature would be available. That's why I explicitly mentioned need of independent verification. It's impossible to verify every sel

Sure, the very same day such feature would be available. That's why I explicitly mentioned need of independent verification. It's impossible to verify every seller out there, but individual sellers can be verified. Those tips must be merely signals to focus, never to penalize a seller solely based on the flags. Also, the existence of the checkbox itself must have some chilling effects on the sellers by changing their risk perception. Those days it's just a common knowledge that those "leave us a review and we'll reward you with a $X gift card" is not penalized in practice. A checkbox with a PR campaign would send a contradicting signal, making this practice more scary. A resourceful fraudulent sellers' cabal (if there are such things) could try to poison the well by paying users to tick this checkbox in random reviews (wasting marketplace's resources by muddying the waters), but this doesn't sound scalable and doesn't feel like a realistic scenario.