The strange duel between Luke and a spectral vision of Darth Vader was a very guarded scene during the production of
Empire. While the Japanese version is fairly faithful to what happens in the movie -- albeit, Kudo added a bit more gore to the decapitation -- the American version has a number of prominent differences.
The US version no doubt had minimal reference photography, since Lucasfilm kept this scene under wraps. Hence the artistic license taken in having Luke duel shirtless. Secondly, it's likely the Comics Code Authority would have prevented Al Williamson from drawing an actual decapitation, no matter how symbolic or surreal it was meant to be. As a result, the Marvel version has a somewhat unsatisfying conclusion to the duel, with Vader's helmet simply falling off and revealing Luke's face.
