DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
utterances - A lightweight comments widget built on GitHub issues.
Commento - A fast, bloat-free comments system to foster discussion on your website
giscus - A comments system powered by GitHub Discussions. Let visitors leave comments and reactions on your website via GitHub!
Hyvor Talk - The Best Commenting Platform For Your Website
Facebook Comments - Facebook comments plugin lets people comment on content on the site using their Facebook account.