Hi all,
If you delete a contact from the address book it does not remove them from the event at the same time; however, it does remove the link from the invitee record (event-level) to the contact record (address book-level), because the contact record does not exist anymore. This results in what we call an "orphan contact." This means that you will be unable to run any contact-level event history or reports related to this invitee.
Because of this, we never recommend deleting a contact from the address book.
If someone has registered for your event, you are unable to delete them from the event. This is because they have that registration data tied to them, allowing you to run reports on no-shows or cancelled registrants. If someone registers for your event and can no longer attend, they should move to cancelled status.
Best,
Julia