[tbworld]

I posted a global form of this earlier on a similar question.
Create plugin at hook: newthread_form_complete

PHP Code:

 //Hook: newthread_form_complete
   global $show;
   $show['additional_options'] = FALSE; 


This will be effective on all styles. Additional conditionals should be added to exclude styles or user-groups. Really no need to edit the template, but good work @arrarrgee and thanks for sharing.