Product Hunt Reviews Widget - Embed and encourage PH reviews into your product
DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
Reviews for iOS - Keep track of your App Store reviews
Hyvor Talk - The Best Commenting Platform For Your Website
Typical Contents - Wirecutter for clothes
Commento - A fast, bloat-free comments system to foster discussion on your website