Darth Vader gives respect to his former Master.

"Obi-Wan has taught you well," says Darth Vader in "STAR WARS: RETURN OF THE JEDI" after observing Luke's strategic position of having the high ground advantage in their duel. This line is a reference to a similar statement made by Obi-Wan Kenobi in "Revenge of the Sith," when he declared, "It's over Anakin -- I have the high ground." This moment marked a crucial turning point in the battle between Obi-Wan and Anakin, as it gave Obi-Wan the upper hand and allowed him to defeat his former pupil. The phrase "having the high ground" has since become a iconic part of Star Wars lore, symbolizing the importance of having a strategic advantage in combat. The mention of Obi-Wan's teachings by Darth Vader highlights the respect the Sith Lord has for his former Jedi Master, as well as the skill and training Luke has received from Obi-Wan.

[damiancruz]

"As it gave Obi-Wan the upper hand"
Was that a pun

[audience]

Despite the wish of the Emperor, the Anakin part of Darth Vader could not put aside his connection with his former Master Obi-Wan Kenobi. Throughout the trilogy he kept mentioning him.