wpDiscuz 4 comes with custom comment form creating function. Once you updated or installed wpDiscuz 4 it’ll generate default comment form with standard comment form fields. You can see and manage all comment forms in Dashboard > Comments > Forms admin page.
The user interface of custom comment form creator is very easy. You can add cols and rows then add custom fields. Example video: http://wpdiscuz.com/400/wpDiscuz-Custom Comment-Form-Builder.swf