This is pretty picky (in keeping with the nature of this thread), but Mister DL Platinum boards and gets "Hello Mister Surname, thank you for being a diamond member" or something thereabouts. I board, as VS Gold, and get "Hello Mister Surname" - the same screen they read "platinum" shows me as VS Gold.
Is it too hard to say "thanks for choosing to fly with us?" (yes, yes it is).
I may not be a DL elite, but i am an elite on a partner airline which you also own a portion of to drive traffic to DL directly. I don't explicitly have to fly DL.