I feel that the ability to leave reviews should be restricted just to those who have actually purchased the content, similar to the ability to add a rating requires that the content was purchased first.
As for the reviews, I myself have made several purchases based solely on what others have said about the content and without which I would never have spent the money on the content. Without the reviews from people who have actually purchased and used the content I don’t feel as confident on making a purchase without them. I have rated and reviewed every purchase I’ve made beyond the Epic content so that others could get an inside look from someone who has had time with the content and I have left both really good reviews and I have left some that I wouldn’t say are bad but they could be seen as helpful for both the creator and for anyone looking to purchase the content. My worst review was simply pointing out that I wouldn’t purchase the content except for purely educational reasons, because the content didn’t actually work out of the box as it was advertised to do in the video demonstration but required several long hours of tinkering to get it to function the way it did in the video.
I think the idea of an “Amazon” style rating system would be a great feature to have and with some kind of motivating force to get people to participate would be nice as well. The star system as it is leaves too much out and since not everyone uses it, it also makes it seem like no one has purchased the content before. On the consumer side I would not want to make a purchase without having the ability to give feedback that could either improve the content for everyone by giving suggestions or give gratitude to the creator for such fine work. I have never purchased through the launcher before simply because it doesn’t show reviews or the ratings, those have been hugely helpful in decision making when it comes to making purchases, same as it does on Amazon. If something has no ratings and no reviews on Amazon I would much rather look further down the line for something that has more ratings and a few reviews to get a better idea of exactly what I would be purchasing.
Just my thoughts on the matter.