A FlyerTalk Posting Legend
Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 100,369
DL seems to permit anyone to buy two seats for any reason. Some other carriers, IIRC WN for example, require that the person be too big for one seat.
Maybe DL ieventually permit one to buy something like one and a half tickets or pay a fee (although Frontier got bad publicity for this policy and dropped it) to guarantee an empty middle seat, or DL could just promise to block middle seats in C+ or create the equivalent of EuroBusiness cabins and fares.