In addition to the above post, I'd like to know how to request a Comfort+ seat during OLCI. Both pax on tomorrow's flights to BHX-AMS-MSP-DEN are FB Gold & Plat elites, but C+ always showed as a cost option in Delta's My Trips.

Unhelpfully, DL's website redirects to KL for OLCI; KL gives no access to C+. I sent DMs to KL & AF's Twitter accounts, who said talk to DL about C+ issues. I sent @Delta a DM, who replied that because I've checked in they can't change my seats.