silk road was on the dark web, a place that is oriented 100% around anonymity. This precludes any sort of "elimination of fraudulent reviews" since there's no reasonable way to build any sort of chain of trust.
I explained several ideas to eliminate fraudulent reviews in my comment, that you didn't address. The main thing is to make a review coupled with a purchase that involves a large cut to the platform, so each review is very expensive. Secondly, don't take reviewers themselves seriously unless they've also made a large overall number of purchases to a diversity of sellers- making becoming a credible reviewer also expensive.
