Specifically, let say I am on a receiving end of reviews made by some random people. I don't really care what they have to say unless it's credible or representative.
Let's look at latter, as it's an easier one. The way to ensure a review is representative, is to ask other people to look at the review and say if they agree with it or not. Once it gets 10-20-30 meta up/down votes, it'd be more or less possible to say if the review is meaningful or if it was a brain fart.
Make the meta reviewing process mandatory. You want to get your site reviewed, pull a "meta" duty on a dozen of past reviews and (perhaps) write a review. When selecting a review for meta, do it randomly, but favor those with low vote count and controversial ones (over those voted way up or way down).
This would be an MVP of your idea. Without this, it's nice, but it's generally useless.
(edit) Oh, and perhaps simplify reviewer's life a bit and have 3 sections - "what's good", "what's bad", "free-form comments".