[kh99]

I don't think there is an existing variable. You could write a plugin using hook location newpost_notification_start that sets a variable, then insert it in the phrase. I took a look at that code (in function exec_send_notification() in includes/functions_newpost.php), but it doesn't look like the group of the replying user is available, or even the userid in some cases, so you might have to do a query to look up the information by username.