Originally Posted by
MSPeconomist
As you seem to have discovered, D is a business class code for international flights.
It looks like you were upgraded but no one told you. Maybe the GA didn't bother or maybe the GA gave your upgraded boarding pass to someone else, perhaps a friend. Unless an insider here can verify some other explanation, you should report the facts to DL.
I thought boarding pass shenanigans would show up as coach/business for the paid/flown instead of the business/coach that it is showing for me?