Sort query by author: 1 author, then others

You could do that with a custom posts_orderby:

add_filter( 'posts_orderby', 'wpa58715_posts_orderby' );

function wpa58715_posts_orderby( $orderby_statement ) {
    if ( is_post_type_archive( 'article' ) ) {
        global $wpdb;
        $orderby_statement = "FIELD($wpdb->posts.post_author, 42) DESC, $wpdb->posts.post_author";
        return $orderby_statement;
    }
}

Swap in your author ID for 42.