I'm not sure if this is an issue for blogspot blogs, but it definitely made the difference for me. I couldn't find this problem addressed anywhere else.
Just in case, I'll back up a little and set this out step by step:
1) Go to Settings, Comments, and select Yes by "Show Comments in Pop-up Window."
2) Go to Site Feed, and if you haven't already, choose Advanced Mode (or whatever isn't Basic Mode).
3) Choose Full by Blog Comment Feed.
4) Republish your blog.
5) Your comment feed will be at http://www2.blogger.com/feeds/YOURBLOGID#/comments/default . You will need to replace YOURBLOGID# with your blog's ID, which you can find in the URL anytime you are in the Dashboard. (You can also get it by looking at the comments on your blog and checking the URL in page info.)
Once you have the link to your comments feed, you can go to Feedburner and burn your new feed. Post a link to it in your side-bar or email it to all the readers who have been begging you for a comments feed!
This Post was written by SusanV from Fat-Free Vegan Kitchen