In ascending him, you are confirming his core fear - that he is not enough just as he is, that he needs to become more powerful to earn respect. He does not even know how to be a better vampire ascendant, because the behaviour blueprint he has is shit. Meanwhile, if you convince him not to ascend, you are showing him he is worthy of love just as he is, he does not need to become an improved version because this version is what you love.
I find it fascinating and awesome how differently and in so many ways Astarion can be interpreted!
To me it was giving him everything he wanted and allowing him the freedom to choose for himself and be responsible for his own actions - even if he may regret it later (which he clearly doesn't). I did the same for all companions - stayed silent or gave neutral responses telling them they could do what they wanted with their life. Everyone's life is their own business after all. The fact that Astarion has to be persuaded out of the ritual (unlike Shadowheart and Lae'zel for example when making decisions during their own storylines) means that he never changes his worldview and desires because of game events and Tav's influence, and in this case Tav is telling him what to do, which I don't feel they have the right to do. He's suffered for centuries, wanted to live his life on his own terms and achieve his vampiric dreams and then Tav shows up, they spend a couple of weeks together and suddenly they know what's best for him? He should totally focus on his own needs, live a full life and not self-sacrifice for a relationship that may or may not even end soon. Personally, I don't see versions of him, I see him as a whole and full package - both dark and light. We call him spawn and ascendant for reference but in essence he's still the same guy, just someone who made different choices. Persuading him feels like Tav asking him to be a good hero because they want him to behave in a certain way (he doesn't want that and straight up tells Tav he can't be what they want to see in him and that he's not a fairytale prince). The game even shows several examples how "well" and "sweet" self-sacrificing and doing the 'right thing' often ends up on a personal level in the end:
Wyll becomes a devil and may end up bound to Mizora forever, Karlach becomes a squid and loses her soul becoming an imitation of herself, Shadowheart loses her parents before she can enjoy a life with them, and of course the dreadful, hated scene that should totally be changed where Astarion ends up burning in the sun while his so-called friends mock him when he runs away.
On another note, since the companions are getting their own unique kisses, I'd like to see Astarion get the same treatment and even have two variants after dealing with Cazador - one for ascendant and one for spawn. We deserve it after how dirty patch 4 did him.
