The temporary super user is a regular Joomla user. We just keep a record of the ID and the expiration date in a database table so we can revoke the permissions and disable the user account at the set expiration date and time.
The user creation goes through Joomla's API — doing anything else would very likely result in Admin Tools being delisted from the Joomla Extensions Directory as a core hack. All the information we ask you to enter is what Joomla requires and it's passed to Joomla's User API. Joomla decides whether to send an email or not. This is part of the core Joomla code and cannot be overridden.
Regarding the user note, well, Joomla does have a user notes feature and the temporary administrator is a regular Joomla user... so you can just use the built–in Joomla user notes feature to add a note about why this user was created :)
Nicholas K. Dionysopoulos
Lead Developer and Director
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