DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
Schnack - Schnack is an open source commenting system written in JavaScript.
giscus - A comments system powered by GitHub Discussions. Let visitors leave comments and reactions on your website via GitHub!
GitHub Team Discussions - Now there's more space to talk through your projects 💬
utterances - A lightweight comments widget built on GitHub issues.
Product Hunt Reviews Widget - Embed and encourage PH reviews into your product