Originally Posted by
NoLaGent
... In regards to the premium seat charge and inability to transfer it to a new flight, AS is not alone in this policy. Whether it's E+ on UA, or MCE on AA, the rules are the same across the board. Seats are non-transferable and valid only on the flight purchased.
DL, however, treats Comfort+ as a separate cabin (W) for pricing purposes, and with a paid W ticket you can SDC onto any flight which has W availability ...
caveat is that a “C+ seat upgrade” appears as S, and the SDC rules of the underlying coach fare apply