Not sure what you mean by "more formatting". You can use HTML in comments - is that not enough? Geeklog filters out a few of the HTML tags and attributes, but you can always allow more.
Well, "enough” to me would be full wysiwig support with a non-html bbcode backing. That would be for complete security. I was most interested in having a forum like environment throughout the CMS like in comments and PM’ing. This, with the option to have the full forum look or just a simple link to the users profile.
Is there a mod for something like that? I know there is with PHPNuke. I don’t like PHPNuke, though.