Yes, you need a G+ account to be able to comment here.
No, this is not intended as an incitement for you to get a G+ account if you don't already have one.
It is a result of the creation of this blog as a means to test integration between a blog and a social network.
Openness for comments here is even less limited than at my "first" blog Theoria magiae non est magia mere theoretica (ut probatur) , where you have to be not only an LJ member, but also to be on my flist there to be able to comment. (I opted for these restrictions there because - quasi - all of the meaningful comments I got there came from people on my flist there anyway; the rest was spam in more than 90% of the cases).
If you feel that you want something published as a comment here and do not have a G+ account: you might want to send me an email (probably best to my office address [ email@example.com ], as I expect that most such comments will be concerning posts on Renaissance intellectual history, DH, academic politics, etc.).
I won't promise you that I'll publish your comment, but I will consider to do so.