GetSatisfaction - Get Satisfaction is the leading customer engagement platform that helps companies build better relationships with their customers and prospects, through the best online customer community.

DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.

UseResponse - Open-source, self-hosted customer feedback software, live chat and helpdesk system that you can install on your server. Organize documentation using knowledge base and get feedback from social networks with centralized system

giscus - A comments system powered by GitHub Discussions. Let visitors leave comments and reactions on your website via GitHub!

UserVoice - UserVoice integrates easy-to-use feedback, helpdesk, and knowledge base management tools in one platform that empowers users to speak and companies to understand.

utterances - A lightweight comments widget built on GitHub issues.