The help for Postorius templates doesn't mention the substitutions available with personalization.
When messages are personalized or VERPed, several extra substitutions are available. These are $member, $user_email, $user_delivered_to, $user_language, $user_name, $user_name_or_address and for backward compatibility, $user_address.
At least some of these should be mentioned in the help.
Edited by Mark Sapiro