Just yesterday it seems (okay, to my knowledge it really was yesterday) that the only way to subscribe to comments on a Blogger or Blogspot blog was to click on the link posted at the bottom of all post pages:
But now on the Blogger comments window, they’ve added a new option, if you’re signed in:
Subscribe to Comments is one of the most-requested WordPress plugins. Now it looks like Google has integrated that popular feature into its blog software.
If you’re hoping to turn this off for your Blogger-based blog, for now it looks like you’re out of luck. There doesn’t appear to be any control over the setting in Blogger. However, rest assured that only signed-in users can subscribe to comments.