Just my opinion.
KiXtart is just a scripting language. You can download the v4.53 package here. In the package is a readme explaining all commands, functions, macro's etc.
You can compare KiXtart with VBS that is native available in Windows.
KiXtart was and is used in many cases during logon to run logon scripts.
Scripting langages are not created to steal credit card numbers and passwords.
Reading emails, well, in exchange, there are ways to backup and restore mailboxes and link a mailbox to a user account.
Much can be achieved by the level of admin rights a person has. One can always abuse these privileges. Scripting languages can also be abused.
I think, in your case, if you think your network administrator is abusing his privileges, you should inform asap your and his superiors. These things cannot be tolerated and have to be investigated.