Well, all I did was look in the postbit template, the variable which calls the username is $post[username] - no surprise there, but further down there is the profile variable - $post[profile]. All you need to do is find the exact code that this var poits to and apply it to the username var. There is a template called postbit_profile which turns profile.gif into the link, all i did was use this and apply it to $post[username] instead of profile.gif.
Once you've got the right href...
<a href="member.php?s=$session[sessionhash]&action=getinfo&userid=$post[userid]" target="_blank">
You can apply it to anything you like to turn it into a link....
In the postbit template, find:
<normalfont><b>$post[username]</b></normalfont><br>
and replace it with:
<normalfont><b><a href="member.php?s=$session[sessionhash]&action=getinfo&userid=$post[userid]" target="_blank">$post[username]</a></b></normalfont><br>
;)