The very fact that this discussion is going on shows that it doesn't make sense in the way that it should. Patbuddha's rationale is the best I've heard and it really does make sense, when you think about it - but it's still a rationalisation. The point is you shouldn't need to think about it - it should make sense instinctively, which the Shaw ghost does and the Christensen ghost doesn't.

This was clearly done just because it could be, and cannot possibly be excused under the "original vision" banner. There was no technological limitation preventing the use of a young actor to play Anakin's force ghost in 1982.

This is actually the worst crime against the OT - even worse than Han shooting second - as it makes the OT not able to stand alone without the PT.