This is making the decision of whether to ticket a partner flight as a DL codeshare or not so very complicated. For some privileges, such as picking certain seats in advance or using miles for a SkyTeam upgrade award (from full fares), the flight must be ticketed under the flight number of the operating carrier, but for other stuff--such as elite bonus miles we're now discovering--one must use the DL codeshare.

Again, the typical DL customer is completely unaware of these subtleties, let alone the rule changes that we're discovering without them being announced by DL.