I set up this blog to work with Facebook comments, using the advice here. The major option for adding comments to a GitHub site seems to be to use Disqus, but for some reason I have reservations about that. I think possibly because I have never bothered to comment on anything which uses Disqus, and I get the feeling it’s not just me. On the other hand, their interface seems generally well-designed (for example, it makes it easy to login with social media) so idk if I have any objective complaints. Some informal polling results suggest Disqus may be slightly more popular than Facebook, but neither is as popular as having a native, more traditional looking comment form.
So maybe neither Facebook nor Disqus is the answer. I did find some other options: 1, 2.
The upshot is that while Facebook comments are set up and hopefully work (test them out below!), that could be a mistake on my part and may change soon. I’m not really expecting too many comments in the meantime.