each time I've been invited on my starter account I've turned it down since I didn't want the chance of having my saved but not uploaded data corrupted.

Anyone want to test this with clean (empty) CensusPlus file?
Either
A: nothing happens and you continue running census on the logged in realm in spite of supposedly having moved to another realm.
B: CensusPlus spots a problem and barfs to a stop.
or
C: worse case.. Census continues to run and collecting data on the new realm but since I have no clue how to tell the program it still assumes it is on the loggin in realm and the data collected is all wrong.
If you haven't see CRZ group joining, you are given a warning notice {That you might be moved to another realm} when the group leader issues the invite.