I suspect “DK” are the initials of the slush reader who rejected my piece.
But I like to think this reads: “Sorry OK”.
As in: “Sorry, OK, we hate to do this, but OK, the thing is, your work is really awful, like criminally bad, so please don’t send us anything else … OK?“
You don’t have to be sorry. You took the time to scribble something in pencil on my rejection slip, thus ensuring its enshrinement in Letters of Rejection. Really, I should be thanking you.