Gonna have to disagree with you Burbin. I don’t really see that symmetry being an issue since both lines are said by Kylo and are only a portion of the truth (remember how Han clarifies it’s his memory?)
And since Palpatine says, “Kill me, and my spirit will pass into you, as all the Sith live in me” it’s quite clear that he’s the real deal, despite Kylo’s insult. Sure, maybe he should respond to his comment, but I don’t think it’s absolutely necessary.