I've heard that before, too. Someone once posted that DL could give you the itinerary # they use for your reservation on a Delta/AF codeshare, but every DL agent I've asked has told me there's no such thing.

I have never flown AF on a Delta codeshare in the seat "assigned" by Delta. I've always been assigned a different seat at check-in (sometimes better, sometimes worse).

The last time Mr. Tb and I checked in at CDG (having been "assigned" a window/aisle combo), we got boarding passes for the 2 middle seats in a row of 4. The desk agent said they were still holding the better seats of AF elites (we're only DL FOs).

Fortunately, the gate agent was very cooperative and found us window/aisle seats.