People online are seeking out social proof. In fact, social proof has become such a trend these days that every online retailer should be thinking about it.
When used the right way, comments can become powerful pieces of social proof that turn your page visitors into buyers.
70% of people trust the opinions of other consumers posted online. (Source: Nielsen.com)
As you certainly know, one of the pillars of eCommerce is trust. Trust between your brand and your customers. Comments provide third party insight into the product/experience you provide. Genuine comments from your Facebook posts or ads will encourage customers to look at you as a trustworthy store. A store they would buy from.