Why Anakin looks like ROTS Anakin in ROTJ..

That's actually a good idea!

 

So essentially, it's like The Matrix. In the real world the characters are bald, malnourished and have plugs on the tops of their skulls. In the Matrix however, they are an avatar of their projected self...And at that point in time everyone's projected self had super cool sunglasses.

It's a great explanation. I've been little unsure of the reasoning behind making him look so different but this satisfies me.

Only one question remains for me...why doesn't his projected self still have the green lightsaber?

 

What Else Was He Supposed To Look Like, A Burnt Corpse With No Limbs? I Don’t Think The Sebastian Shaw Version Made Sense

 

I've assumed people thought this for a while.

It makes sense to me. Even in A New Hope, we talk about how Anakin died. The Jedi's death and Vader's birth seem interlinked.

I'm not sure how I feel about how that affects ROTJ, though. While it makes sense that Anakin would associate his younger self with himself as a Jedi, I'd like to think that he did turn back to the light before the end, and it was nice to see that reflected with an older force ghost.