ok i dont know cus never used IPB but logicly it should be like this

go to the template folder and search for something like dysplay.template.php, its called like than in SMF anyway you have to search for it if you cant find it attach the template please and ill try find it for you

anyway when you find the template just serch (Ctrl+F) for a line ?showuser=
There will be a couple results just find the one that looks like $boardurl?$boradurl

ANYWAY if you can just attach the template and ill do it for ya