I'm surprised you need a plugin to show the ranks. But anyway.... if you want to change the code just for the PM page, you may use this condition:
PHP Code:
if (THIS_SCRIPT == 'private') { rank code without <br /> between all ranks }
However, if that code is being used in posts and it is fine, then my guess is this is a CSS issue. The only way to check that out is to be able to view the actual page using a tool like firebug. Are you familiar with that? You may view the CSS and perhaps make a div wider.