Just tried to book Business Class HKT to MSP via ICN & JFK on December 27, 2015. The first two legs are KE flights. Shows availability online and when you try to finish the booking, error message. Called Delta and they saw what I was seeing, but said there is no way around it, it is Korean blackout dates.
They shouldn't be showing this as available if it's really not. Started to make other plans based on that flight route.