After playing with Ghost for a couple of days I still haven't figured out what to do with comments. Ideally I want something like Wordpress' built in system, where you can post "anonymously" without registering and still get updates by email.
I have read a few blog posts recently that made me look at using Twitter for comments. That might work out for me, since I use Twitter so much, but not if I'm to use Ghost for other people's blogs.
After I realised that Disqus allows commenting without signing up I thought that might be a good fit. But they do not support notifications without signing up, and I do not want my readers to have to sign up to Disqus, so it's not a perfect fit for me.
Since I want readers to post without signing up Facebook and Google+ comments are out of the question. It doesn't help that I rarely use the services myself.
Then we have Discourse, but last time I looked it looked too focused on creating a "forum", and not a comments system. I'll have a new look at Discourse tomorrow.