Comment on WordPress Gravatars by SEO Dave.
I’ve used the plugin you mentioned above “Extended Recent Comments with gravatar” as a starting point for a new Stallion SEO theme built in plugin for Stallion 6.2, might also release it as a stand alone plugin when I get the time, not seen a better recent comments plugin with gravatars and excerpt built in that’s SEO friendly.
The Stallion WordPress SEO Recent Comments with Gravatar Plugin creates a widget that has the latest comments with a gravatar image, link to the comment and a short excerpt of the comment. Removed the link to the comment author site as it’s SEO damaging.
Looks good, when I start updating my sites with Stallion 6.2 you’ll see it on the sidebar on this site as a replacement for the current recent comments widget.