Humility has never been a trait that any of Feanor's seven sons, or indeed, Feanor himself, ever had in abundance. Maglor has learnt it, over the years, but he is still his father's son, and he smiles a little smugly at his uncle's response. This is what he was always good at, at manipulating the emotions of his audience, at knowing exactly what it was they needed to hear. If he had wanted it, he would have been a terrifying High King, but that was never what he wished for.

"Then take it as a gift uncle, in thanks"