It would be great if TripIt had duplicate detection for flights.

I've set up certain Gmail filters to forward messages from various email addresses with certain subjects to TripIt. These rules aren't perfect, but they get the job done, but that means that whenever an airline like Virgin America sends me details of an upcoming flight (that I already entered into TripIt), it gets forwarded on to TripIt and recorded as a new flight, even though all the flight details (including confirmation number!) match.

Why doesn't TripIt recognize these as duplicates and either ignore them or save them as activities to moderate later: "Looks like this is a duplicate of a trip you've already recorded. Would you like to overwrite the old trip or discard the new one?"