Currently bugged Epilogue dialogues if you were in a romance with (spawn)Astarion but left with Karlach for the hells:
Astarion: And look at you! Straight from the Hells, still reeking of brimstone. I take it you've been having fun?
Player: A little. But I have missed you.
Astarion: And I have missed you. But I understand - our favourite fiery tiefling needed you. So do what you have to. You know where to find me when the mission's over. [Devnote: Speaking to a romantic partner who left to fight in the Hells. Astarion has missed them, but supports what they're doing.]
To me this is indicative that he's grown as a person. Also who knows how this line is delivered as it's currently bugged.
I did expect him to be hurt, but the game has been very adamant that six months post story spawn Astarion is no longer passive aggressive dipshit person.
In my opinion the mature reaction after 6 months would be to say "I am sorry. I understand why you did it. But our relationship is over. I hope things are going well for you and Karlach." (Like I explained in my other reblog, I consider this abandoning your partner because there is zero communication, the final scene doesn't even play with the love interest. The main character just leaves behind their back.)
So to be clear… I don't think he should throw a hissy fit in the epilogue after 6 months. But he also shouldn't forgive this so easily.