Astarion hadn't had problems with anyone's identity as long as he could remember. He was raised a stuck up elf, and while a part of him clung to those old beliefs, he was a vampire now. He barely remembered what his personality had been before he had been turned. Even more so now; though, he wouldn't bat an eye at what anyone identified as. He'd seen it all while under Cazador's thumb, and he continued to see more now that he had a tadpole nestled in his head.
When it came to you, his everything, his love, his partner in life -even if his was long gone, and even if they died before he was able to rest his head along side theirs- he would never have questioned a single thing they said to him about their identity. What did it matter? If their pronouns changed every day, every week, every year, if they'd changed since he first met them, or if their pronouns hadn't changed since they were young, he wouldn't give two damns.
Others, however, seemed to struggle with the concept a little more. Astarion had sent Wyll several glares while the other man recalled a story. The Warlock kept using the wrong pronouns for you, and you had been too polite to interrupt him and correct him, "You know it's not rude," Astarion gently cooed in your ear, pressing a soft kiss to your forehead, "I love you, darling. Exactly as you are, not for what he assumes you to be."
The vampire had pulled you out of camp while Wyll was still going on, his hand grasping yours tightly and his mouth pulled into a bitter frown, leading you instead to a nice clearing near the head of the stream, "This seems like the perfect spot to be alone for a while, yes?" he glanced over at you and raised his eyebrows, "Would you like to talk about what happened, or ignore it? If it's the latter I'd be happy to instead discuss myself. I do think any self respecting person should leap at the chance, and if it would put you at ease to hear my voice going on and on, well my dear it would be my pleasure."