Q: I have an eCommerce site and want to know how can we differentiate between thin & rich content, so as to avoid thin content penalty?
A: If you have a high domain authority, Google will look at the thin content in an other way. The best example is eBay, which managed to escape from the eyes of Google for many years, despite having thin content. It has now been hit by Panda because I think they overdid it. There were hundreds of millions of pages with thin content (almost 98% of the site).
A legitimate SEO strategy is what I believe will be the best if you are worried about thin content. It will help you in earning more high value links, increasing the domain authority, and also reducing the thin content risk. You can implement some learning from Amazon, which makes its computer generated product pages less thin by adding product reviews, which on the other hand also add value in form of user-generated content.