AuthorHighlight - WordPress Plugin Repository - Trac
dev.wp-plugins.org/wiki/AuthorHighlight
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Author Highlight is a plugin that prints out a user-specified class attribute if the comment is made by the specified author. It is useful if you would like to apply a different style to comments made by yourself.