Basic idea of using GitHub issues as a commenting system for a blog.

This only includes a link to the respective issue on GitHub itself, where people can read and write comments.

It could conceivably be extended using the GitHub API to include the comments from github on the blog page itself, and either allow commenting straight from there or provide a link to the actual issue page on github to write the comments
(in effect emulating a readwrite permission on the post, or a readonly permission)