I don’t have a picture of this right now, but after Vader throws the emperor down the shaft, it’s pretty obvious his hand is underneath his too-long sleeve. You can even see his wrist is bent. It’s a small thing, but one that bugs me every time I watch the movie.
You can even notice Vader’s too-long sleeve with the wrist bent afterwards in the shot when Luke pulls him away from the shaft.
Luke had the same problem in Empire