The official novelisation of Star Wars: Return of the Jedi gives us a pretty clear impression of the Emperor's feelings on the subject of Kenobi's death
- He was pleased that an enemy was dead
- He was pleased that his apprentice (Vader) had done the dirty deed
- He was pleased that Luke was no longer receiving training from a Jedi
Basically he was just really quite cheerful about the whole thing, bordering on smug
“Tell me, young Skywalker,” the Emperor said when he saw Luke’s first struggle had taken its course. “Who has been involved in your training until now?” The smile was thin, open-mouthed, hollow.
Luke was silent. He would reveal nothing.
“Oh, I know it was Obi-Wan Kenobi at first,” the wicked ruler continued, rubbing his fingers together as if trying to remember. Then pausing, his lips creased into a sneer. “Of course, we are familiar with the talent Obi-Wan Kenobi had, when it came to training Jedi.” He nodded politely in Vader’s direction, indicating Obi-Wan’s previous star pupil. Vader stood without responding, without moving.
Luke tensed with fury at the Emperor’s defamation of Ben — though, of course, to the Emperor it was praise. And he bridled even more, knowing the Emperor was so nearly right. He tried to bring his anger under control, though, for it seemed to please the malevolent dictator greatly.
Palpatine noted the emotions on Luke’s face and chuckled. “So, in your early training you have followed your father’s path, it would seem. But alas, Obi-Wan is now dead, I believe; his elder student, here, saw to that—” Again, he made a hand motion toward Vader. “So tell me, young Skywalker—who continued your training?”
That smile, again, like a knife. Luke held silent, struggling to regain his composure.
The Emperor tapped his fingers on the arm of the throne, recalling. “There was one called … Yoda. An aged Master Jed … Ah, I see by your countenance I have hit a chord, a resonant chord indeed. Yoda, then.”
Luke flashed with anger at himself, now, to have revealed so much, unwillingly, unwittingly. Anger and self-doubt. He strove to calm himself—to see all, to show nothing; only to be.
“This Yoda,” the Emperor mused. “Lives he still?”
Luke focused on the emptiness of space beyond the window behind the Emperor’s chair. The deep void, where nothing was. Nothing. He filled his mind with this black nothing. Opaque, save for the occasional flickering of starlight that filtered through the ether.
“Ah,” cried Emperor Palpatine. “He lives not. Very good, young Skywalker, you almost hid this from me. But you could not. And you can not. Your deepest flickerings are to me apparent. Your nakedest soul. That is my first lesson to you.” He beamed.