Seems that Google has been doing "upgrades" to their software. Anyway, I've noticed that the ability to follow comments has disappeared on a lot of blogs. If you're having this trouble on your blog, you might want to switch to the "embedded" comments. See here:
Also, if you are having trouble posting comments on Blogger hosted blogs, it may be your version of Chrome if you are using that. See here:
Google use to be much better about these things until they started their push for G+.