Originally Posted by Nyloth
Astarion has a dialogue about the stars, where he is clearly interested in your company. It's funny, but you can also flirt with him in this dialogue, but I don't think it affects.

Yeah, about that... he does seem interested in your company, and the MC clearly takes it that way and can flirt back, but the writers were going for... something else (I'm being vague here because datamined spoilers). Of course we, as players, can interpret that scene however we like; what the writers intended isn't the be-all-end-all of meaning (and maybe things had changed by the time they actually got around to recording the scene, I dunno).

That said, I don't have any problems with Astarion's "romance" at all. His advances definitely do not come out of thin air at the party - I'm more surprised he waited that long!