I don't know, I'd still argue that Vader, while not being pure, was only able to appear as force ghost at the end of rotj as a result of his sacrifice to save Luke. His intentions and actions then were 'purer' than anything he'd done before, even before he turned, when he wa mostly angry and self serving. The six films are all about his fall, and eventual redemption - in the original version of rotj, having him appear alongside yoda etc shortly after his death confirmed that he'd truly been returned from the dark side.
(Also, I always assumed that the title of the film did not just refer to Luke in that respect).
Having young Anakin there just appears to be the result of Lucas making another clumsy attempt to link the prequels into the ot. Imo anyway!
This post has been edited by Traveller: 03 January 2017 - 09:54 PM
So that's the story. And what was the real lesson? Don't leave things in the fridge.