Comment on SEO Super Comments WordPress Plugin by SEO Dave.
Tried a Gravatar Hovercard plugin with the TwentyEleven theme and the TwentyTen theme and it didn’t work, so looks like the two plugins I found first are broken (first two listed in Google for the “Gravatar Hovercards WordPress” search).
Found a plugin called Extended Gravatar v.06 which works in TwentyTen. Tested on Stallion v7 and didn’t work in the comments area, but did work on the author biography box and if I posted a Gravatar image link within a post. Interesting feature with the Extended Gravatar plugin, looks like it can be set to email your commenter’s an invitation to join Gravatar if they don’t already have a Gravatar image etc… which might fit in well with your plans.
Suspected the issue would be the Gravatar SEO code I use in Stallion 7 that turns the Gravatar image links (which are potentially SEO damaging) into CSS based background images (which are SEO neutral). Changed the code to what other WordPress themes use and it worked.
I’ve left the original Gravatar code within Stallion, so easy to revert it back.
comment_author_email; $size = 60; $rating = get_option('avatar_rating'); $gravtype = get_option('avatar_default'); $default = urlencode( 'http://www.gravatar.com/avatar/ad516503a11cd5ca435acc9bb6523536?s=' . $size ); if ($gravtype=='mystery') $grav_url = 'http://www.gravatar.com/avatar/'. md5( strtolower( trim( $email ) ) ). '?s=' . $size . '&r=' . $rating . '&d=' . $default; elseif ($gravtype=='blank') $grav_url = "/wp-includes/images/blank.gif"; else $grav_url = "http://0.gravatar.com/avatar/" . md5( strtolower( trim( $email ) ) ) . "?s=" . $size ."&d=" . $gravtype ."&r=". $rating; ?> <div class="gravatars" style="background: url()"></div>
<?php echo get_avatar($comment, 60);?>
That should get you on the right track.
If you get something working that you think would extend Stallion would consider adding the plugin to Stallion and add an option to use the original Gravatar code above or I might be able to find a way to have it work with the current Stallion SEO safe Gravatar code.
Do like the idea if commenter’s will use it.