Coment is a tool for monitoring and managing all comments on Facebook, Instagram, Twitter, YouTube, Disqus and WordPress with a single click, all from one single dashboard. Plus, it's for free!
schnack is an awesome, ad-free, open source Disqus clone that comes with a very minimal, hackable code base.
Hosted commenting that's painless to embed, a pleasure to use, and a breeze to moderate.
MyTwoCents Comment Aggregator is a browser extension that puts the relevant Reddit, HackerNews and Facebook comments (for now) on any website with the push of a button. It also shows the number of comments available for the current site on the extension icon in the browser.