In the past I have seen vendors blackmailing or making threats to blackmail buyers; they have this ability because they have your address, or an address you're somehow connected with. They claim they'll tell LE for X reason. X reason being something along the lines of "Don't give me a bad rating or else I'll tell LE about your drug use!"
Well, it sounds like it would be possible to make it where verified buyers can give anonymous ratings using a tool called a ring signature. This could be implemented in a variety of ways, there is some discussion & resources here: https://en.wikipedia.org/wiki/Ring_signature
https://www.reddit.com/r/Monero/comments/6gp0cn/ring_signatures_darknet_marketplace_ratings/
Even if the buyer doesn't leave a rating, it will still contribute to the security of other buyers who opt to leave a rating simply because it will be a bigger pool of signatures to draw from.
What benefit would this have over just making the all names on reviews anonymous?