One way to do it is to add a new class for your links at the bottom of Styles & Tempaltes > Styles Manager > find your style > Main CSS > Additional CSS. See this page for help writing links for a class (at the bottom of the page) -
http://www.echoecho.com/csslinks.htm
Then in the postbit (_legacy) templates, add the class to the div tag surrounding the message - <div id="post_message_$post[postid]" class="myclass"> I think that should work, but haven't tried it.