Realname Comments

Hi thanks for the great module. How would I go about getting the title and comments on my profile page to show the 'default' username alias and not the realname replacement? I've tried a combination of things and I just can't get this to work. Ideally what I wanted to do was allow admin to view username replacement throughout the site and everyone else to view the default username alias.

Another thing that might help is that I'm using the Acquia Marina theme and this is the code displaying the username

theme('username', $vars['comment'])

Any help would be appreciated.