I just release an update of my plugin, called Author Highlight (eXtended Version). (never been release in this forum before).
This is a plugin that prints out a user-specified class attribute if the comment is made by a registered user.
Featured automatic detection for all user, with an option page for easy configuration, and now with additional option to let the plugin automatically put the code to your template.
All you need to do is to edit your CSS file and configure how the CSS class stylish your page. Maybe you want to change the background image or color, change the text or url behave, is up to you, no limit of what you can do.
Base on Jonathan Leighton Author Highlight plugin.
You can download and try it from here.
Thanks and best regards.