ImperialFighter said:
Like others, I thought about removing either "...Luke Skywalker" or "...young Skywalker" from the sentance altogether too, as the 'beat' of the dialogue still sounds good without it, before Vader eventually replies "Yes, my master". But I ended up thinking that without clarification of <span style="text-decoration: underline;">exactly who</span> the Emperor means before Vader responds "He's just a boy...Obi-wan can no longer help him", that the Emperor might reply "Not that brat Luke you fool!, I'm on about ANOTHER enemy we've got to contend with!"
I think that they both know they’re on the same page, but if you don’t agree, then wouldn’t it make sense for the Emperor to “test” Vader? Vader has just said “I have felt it” and “Yes, my master.” Think of the Emperor’s omission of Skywalker’s identity as saying, “Are you just pretending to know what I’m talking about, or do you really? Prove that you do by telling me.” Vader passes the test by saying, “He’s just a boy. Obi-Wan can no longer help him.”