Really? I had no idea. Not trying to be rude or anything but that seems plain stupid to me unless we're talking about a user scenario where users establish a connection one time only and for a long period of time, like a service.
In a common buy/sell/trade user scenario where users buy several products (sometimes from the same buyer), that model just doesn't work.
Imagine if a buyer has one bad experience after successively purchasing a 1000 different items from the same seller, his review will place that seller with -1 point not reflecting his true value.
How can I change that behavior so that users can post multiple non-editable reviews about someone and allowing the admin to delete them?