It's been brought to my attention that people can't comment on any posts at the moment. It seems that clicking on the "Post a comment" link causes a jump to the bottom of the page and doesn't open a comment form.
I'm currently looking into why this is happening: comments are indeed enabled on this blog and I've even temporarily changed the moderation settings to see if that would make a difference. It hasn't.
I suspect it might be something to do with the template. If it is, I'll change it in the next few days. If not, I'll hunt down an answer in the forums. In the meantime, please be patient. Normal service will be resumed as soon as possible.