How to handle Portal duplicates?

Hi, just a short Question:
Sometimes i come across Portal duplicates in Outgress: a moved Portal exists in Outgress at the original and at the new Location. Current example: The Portal 'Kaffee Und Kuchen' exists two times: https://outgress.com/portals/kaffee-und-kuchen.2157390/ is the old location and https://outgress.com/portals/kaffee-und-kuchen.2645903/ the curent one. Now should i mark the Portal in the old location for Deletion or can i mark it as being moved - Or would that cause two identical Portals in the new Location? Or does it make sense to include something like a 'flag as duplicate' so that historical attack data will be merged?