Bingowings said:

Mark turns in a performance consistent with the rest of the films and that's it really.

I strongly disagree with the above statement. Mark's performance is excellent; far superior to his work in the prior two films. It's not so much about what he says, then what he doesn't say. There is just a quiet sadness to the performance that really gets me when I watch ROTJ; which makes the ending Ewok celebration when he sees the ghosts, and that sadness lifts, so powerful.

Maybe I'm reading to much into it. I am a biased defender of ROTJ afterall!