Looking around for this same matter I believe what you are looking for is something like this:
function myUniqueFeedFilter($query) {
if ($query->is_feed) {
$query->set('cat','-1');
}
return $query;
}
add_filter('pre_get_posts','myUniqueFeedFilter');
I hope this helps you.
Actually I’m working on it, maybe by monday I would have this figured out for nginx, Stay tunned! 😀
I prefer, WP-HashCash, or SpamKarma 🙂 of course, this are my preferences…
