The rating system should be removed (for transparency...I have full 5 stars), until OU makes it more difficult to make additional accounts and "shill" each other.
Having the option to down rate flakes is not the solution, as these flakes can just make another account in under 3 mins. Flakes will always be around on every selling platform. There are less of them on eBay because there are financial/legal consequences, but they do get a few chances and the accounts get banned.
I think the problem will solve itself when OU starts charging listing fees, as OU will be forced to protect sellers.