> A review telling me that a seller is doing shady things tells me nothing about the product
It's not telling you anything about the product, but it also making you aware that those other review you thought were telling you something about the product, actually are not.
In essence you are saying that it is a reasonable stance to remove off-topic bad reviews, but keep off-topic good reviews.
I think the concern is -- seller A (or manufacturer) has created lots of gamed reviews for product A. Putting a negative review on seller A is much less visible, and leaves the fake reviews in place, so that when successor-scammy-seller-B sells the product everyone is still deceived.
It's not telling you anything about the product, but it also making you aware that those other review you thought were telling you something about the product, actually are not.
In essence you are saying that it is a reasonable stance to remove off-topic bad reviews, but keep off-topic good reviews.