WP: Customize WordPress' feeds

/*A simple way to supplement WordPress feeds. In this case, adding comment count and categories.

Just add this to your theme's function.php and you're off to the races.
*/

function ulfben_supplement_feeds($content){
    $post_categories = wp_get_post_categories(get_the_ID());
    $cat_list = array();
    foreach($post_categories as $cat_id){
        $cat_list[] = '<a href="'.get_category_link($cat_id).'" target="_top">'.get_cat_name($cat_id).'</a>';
    }
    $comments = get_comments_number();
    if($comments){
        $comments .= ($comments == 1) ? ' comment' :  ' comments';
    }else{
        $comments = 'A penny for your thoughts!';
    }
    $comments = '<a href="'.get_comments_link().'" target="_top">'.$comments.'</a>';
    return $content.
        '<div style="display:block">
            <small>Posted in: <em>'.implode(', ',$cat_list).'</em><br />'.
                $comments.
            '</small>
        </div>';
}
add_filter('the_excerpt_rss', 'ulfben_supplement_feeds');
add_filter('the_content_feed', 'ulfben_supplement_feeds');