Eric and Blogger team has pushed what they called "small-but-crazy-useful new feature" to Blogger which enables visitors to subscribe their email when they give a comments. Before this feature is available, you will have to revisit the website again to check whether your comment has been replied or not. By using this feature, all you have to do is tick the option that will active the feature while you are giving a comment on Blogger blog. Of course, it will only be active when you have logged in using Google account, since it will only use Google account to avoid flooding your email account.
Check the announcements on Buzz Blogger and also in Blogger Help