I booked an itinerary on expedia with 4 Delta segments and two KLM segments, however, all the flights are KL coded.
The KLM site would not recognise my status and hence would not let me select premium seats. On the DL site, I could not even make a seat selection. I figured maybe it will take some time as it was an expedia issued KL coded ticket. After waiting for about six hours I called DM line. The agent said "You are not supposed to be able to see seating charts. Even I cant see them"

I asked her how I was supposed to select seats? "They will be assigned at check in as they are all KLM flights" I pointed out to her that 4 of the flights are on DL metal. But she insisted they were KLM flights. She didn;t seem to know the difference between DL coded and DL operated.

Another call to the DM line and intervention of a supervisor got me seats assigned on all six segments.

The only seats in EC left were middle seats. Doesn't DL save some seats for gate check assignment? According to the supervisor, they release some seats before gate check-in if they are needed.