jmertic: Shouldn't there also be some downgrade compensation?
Also, it's frustrating to hear that DL had planned to rebook feds99 in C+. What was the fare class on the original AF ticket? That should matter more than having AF premium economy 'sound like' comfort plus to a phone agent.
I suppose over time as more Delta Premium Select seats get sold (and IRROPS happen to them) phone agents will start to have experience with these issues. Also points to problems with DL using their various nomenclatures that don't really match industry standards.
And, finally, though this wouldn't work to AMS - but Alitalia also has Premium Econ in addition to VS.