Blog comments are always appreciated and it's good etiquette to reply to someone's comment, or to visit and leave a comment on their blog in return.
Have you ever tried to respond to a comment but the return address is 'firstname.lastname@example.org'? That happens when a blogger hasn't changed the privacy settings. It's very easy to do:
1. Log in to Blogger and click 'Dashboard' on your screen's upper right
2. Click 'Edit Profile' (left side of screen, under your name/photo)
3. Under Privacy, check mark 'Show my email address'. Further down under Identity, type in the email address you want comments to go to (can be different from your log in email).
That's it. Doing this will ensure that when you leave a comment for someone and they hit 'Reply', your email address will show up. Hope this is helpful :)