Unlike Disqus which is third-party, owns your data, and injects a ton of garbage JS assets into your site, staticman is free, open-source, and lightweight.

The workflow is very cool. When the user submits something, staticman submits a pull request to your static sites git repo. If you approve the user content (e.g. a threaded comment), you merge the PR and it becomes live and static as part of your site.

Don't take my word for it. These people also love staticman:

• "I reviewed the best commenting systems for a static website some time ago. Out of several decent options, I have decided to use Staticman as the commenting system of this website."
• "In the months after removing Disqus from my site in favor of a static-based commenting system, Staticman has matured with feature adds like threaded comments and email notifications"
  etc.