[pwiesner]

There is not an option to include the RespondentGUID in exported results. I will add this feature request to the development teams internal tracker.

You are correct these fields are both used to track users; however, they are used to track different types of users.

The UniqueIdentifier column contains a user's UniqueIdentifier. For a standard Checkbox user this is typically their username. For a network user this is typically domain\username. A UniqueIdentifier is recorded for domain users who do not have Checkbox network user accounts.

The RespondentGUID column is a 32 digit hex string and in this case is used to identify anonymous respondents. It is used to facilitate survey options such, as "Maximum Responses", "Responses Per User", "Allow Users to Resume", etc, while maintaining anonymity. This value should be null for registered users.