I, too, hesitate to think of ways ASTARION specifically is harmed by the ritual, besides, "vibes." People decry that their sweet man is gone, but I saw a great Reddit comment that pointed out, if you've already been indulging his whims, agreeing with him, or at least not arguing with him that he needs to be a better person, then his personality won't seem to change at all. So, how is he harmed? I see no evidence that he regrets the ritual in the slightest, that it didn't give him everything he wanted. The only hint of regret I see is if he loses Tav/is never partnered in the first place; he definitely seems lonelier. But that to me doesn't mean he feels the ritual was a mistake, or that it hurt him in any way.
Given that, I'm going to say something that maybe will sound a little unkind to those who are vehemently for the UA path: In my opinion, any harm caused by the ritual is not to Astarion, but to the player who fell in love with the softer, funnier side of Astarion now has to contend with the idea that a lot of that may have been part of the performance; maybe deep down, he's not the sweet pookie they fell in love with. They have to prevent him from ascending, because they have to believe that deep down, he's a good person who secretly wants to do good things, despite the fact that there's really no evidence for it. Even in the face of the "7k" spawn he's making dismissive excuses for the part he played in their fate. Astarion is evil. He has always been evil. I don't think becoming a spawn and enduring torture made him evil. I think that's a completely separate thing.
And the only reason I say this is precisely because so many of them lash out at AA fans and tell us we made the wrong choice. I have seen this on so many corners of the internet, again and again, the same talking points. Coming onto any pro-AA post to "well actually" completely unprovoked, even ones that don't even mention the spawn path, they're just, "here's a cool video of AA saying AA things" or something like that. Any intense reactions like that usually stem from somewhere, and if they can psychoanalyze us, I can do the same to them and say, I think they're projecting their insecurities about the path they chose. I think they realized that both paths for Astarion release some darker version of himself (either the darker version who gets everything he wants, or the darker version who will always wonder what could have been, and maybe seek out another way to get it), but they have to believe that they made the "right" choice (spoiler: there is no right choice because it's not a win/lose game), so they have to tear down the AA path as much as possible.
