I just posted this in trouble shooting:
Is it possible to include the email history in an email sent out? I would like to reply, showing clients what they actually wrote.
Help is GREATLY appreciated, since I am no where near a PHP-expert
This will do close to what you are looking for:
http://www.osticket.com/forums/showthread.php?t=3857(http://www.osticket.com/forums/showthread.php?t=3857)
This only does it on staff assignment, but with a little more help it could be a generic variable to be used in any email template.