He was not jealous, simply annoyed at her lack of interest in him at the moment. Socialization for him went into a far stretch when there was so many people and not all of them dared to know him. They were all mingling. The only mingling he'd ever done had been with fellow warriors, and those that he had given the right to be a part of his direction.
Achilles gave the other man a nod, not quite sure what to make of him. Had he even heard of him? If he couldn't remember than it wasn't worth much, immortal or not.
With Absinthe's move, it indicated that she wanted him to react in some way. He did not, and his voice stayed silent, showing that even the lack of reaction meant something. He didn't come so that she could flutter around like a butterfly all night. He would be a force for her to reckon with if she chose to disapprove of his presence.