Leaving a comment on github is pretty easy if you have ever created a new userid and left a comment on the web before :-). My apologies if this isn't easy for you!
Yes, you need to log in, but if you really care about that comment you wanted to leave, that shouldn't be much of a problem. I decided to go with github issues because if you just want a throwaway comment, you can always Tweet to me (@ mention @rtanglao on twitter) about it and we can both count on that interaction losing traction and being forgotten by everyone in about a day. That's fine, we should be able to have those interactions, just not on the blog itself.
If you want to leave a real comment, one that requires meaningful and direct interaction between you and me (say you a found glaring problem with one of the thing I posted, or you have information that you think would help me update a post or write a new one, or you have real questions after reading a post and need additional information), then this is a much better place to have a conversation that can guide real change to my posts.
Get an account if you don't have one (it's free), and then file a new issue about what you want to talk about - I'll try to respond the same day, because if you care enough to comment, I certainly care enough to engage with you.
p.s. Why github? Because it's fast, updated and has features to lock issues if people sp*m them. And it's a real business with a real business model (charging software developers for private software repositories) unlike the other commenting systems