Star Wars: 14 Crazy Rumours Lucasfilm Started About The Empire Strikes Back In 1980
6. Vader's Mask Is Explained (And Removed)
One of the biggest potential hazards with revealing Darth Vader as Luke's father was that audiences may not buy the foreboding figure as anyway human, so there's a noticeable effort to humanise him in Empire, with Yoda talking about his seduction and Luke's cave vision hinting at the man underneath.
Miller started seeding this concept aheadof time by suggesting the promise of an explanation for why he's in the suit and directly alluding to a scene in the finished film:
It has also been reported that in Empire we learn considerably more about most of the continuing characters including why Darth Vader wears that mask. We have also heard that in one scene we see Vader without the mask!
This is very leading stuff, stoking the flames of anticipation while actually relating little to the finished film; the reasoning behind Vaders mask had been decided by Lucas at this point, but wouldnt be revealed on film until Revenge Of The Sith, while that unmasking scene is only from behind.