I'm in Forsaken cave but was avoiding learning the last word of the marked for death shout since I had only 2 of the words learned when I installed Dawnguard. Before I take on this bug I have two questions:

1) Does the extra drain vitality shout cause any permanent damage to your game? or can you just get by with ignoring the extra glitched shout that appears?
2) If you learn all three words of drain vitality before learning another word of marked for death, does it still cause the glitch? or no?