Legally they are probably correct. However from a customer's viewpoint this is terrible. They probably know how much compensation they are willing to part with, so why not send you a response saying that on behalf of Comair we will be giving you a certain amount of money. They are probably giving you a Delta Dollars certificate anyway, so this is a sham.

BTW, what would they be doing if this was a Song flight? Tell you to sing for your money?