instead of:

// START hack to avoid administrators rel="nofollow"
global $current_user;
if($current_user->user_level > 9){
return $text;
}

to avoid rel nofollow on wordpress for all users, the code that need to be added as indicated for two times in place of the above, are these following two lines of code (one is a comment in true)) substituting the above that avoid no nofollow only for administrators:
function wp_rel_nofollow_callback( $matches ) {
immediately after this line ADD the following code:
// eliminate for all users the rel nofollow addition on wordpress:
return $text;