Comment on WordPress Gravatars by SEO Dave.
It’s using the standard recent comments code that links to the authors URL with a rel=”nofollow” link which deletes link benefit. Also the formatting didn’t work well because the Stallion sidebar links have the little image to the left and so it would need custom CSS for the plugin.
I agree would be good to have a recent comments widget that uses gravatars (without damaging SEO), not for 6.1, but a future release maybe.
Update: added the feature to Stallion without the SEO damaging nofollow links.