ok i guess when i wrote up my threaded comments hack, i did not include the feature where the comment author who you are replying to will get notified by email. hrm it’s just an update in your functions.php under wp-includes.
here’s my code. you can replace your old wp_notify_postauthor function with it.
like always. BACK UP before you overwrite anything.
small bug fix – spotted by ecila 🙂 the reply notification does not include the commenter’s email address so i added it in now.