As much as the mod staff are over-stretched (or rather, under-staffed) and struggle to maintain a presence here, I would like to ask folks on both 'sides' of this discussion to please remain civil to one another, and to focus your attention on discussing the topic, rather than taking jabs at each other or judging each other based on assumptions of personality.
If we look at the reasons behind many of the stated alignments, they differ by creature, amongst undead. Zombies, and the vast majority of other insentient undead, for example, are marked as evil because they are the defiled remains of people animated by necromantic magic; they are insentient (or mostly so0, and instilled with an urge to hurt. Ghosts, by contrast, have the full spectrum available to them because they are the mostly intact spirits of former entities and retain much of who or what they were, including a majority of their personality.
Vampire spawn get the evil tag because while they can and often do retain memories of their past life, they do not retain their former emotions, feelings or empathy; they can, and often do, put on a facade of these things, either in mimicry of a life once lived, or as a means to an end, which is usually sating their hunger, or coveting the physical symbols of the things they liked or enjoyed in life. They are incapable of caring about or for others, and pursue only personal, selfish, physical motives as an obsessive facsimiles of those past feelings. In addition to this, they are incapable of self-direction outside the control of their master, and are only 'mostly' fully sapient; the hunger and the control are larger factors in their existence than their own sense of self.
Astarion's behaviour matches this more or less perfectly, and would give players reason to believe that when he says he cares about something outside himself, it is untrue. Some rules may be broken, but by his behaviour alone, he still seems to be showing the cold, selfish, physically-focussed passion that one would expect of a spawn.
However: As it's been explored, many of the rules governing him have been broken. He doesn't burn in the sun (Larian have acknowledge this as a deliberate change), he is not beholden to forbiddance (they've also acknowledged this). He also does not remain bound to his resting place or the need to sleep under earth (Larian have not acknowledged this and don't seem aware of it), and he has developed a particular unusual vulnerability to wooden stakes (This is ridiculous and stupid, and larian don't seem to be aware of their ignorance). He isn't bound by his master any more, or so he says (we cannot confirm this, but it seems likely to be true).
What does this mean for Astarion's personality? Well... It means that it is certainly *possible* that he has a capacity for change now that he did not have before. For that to be the case, he'd have to no longer bee a vampire spawn in the traditional sense, and it would lad us to ask the question of where his new capacity for emotion came from - the only place it could have come from would be the tadpole, and his transition towards becoming an illithid - they are a culturally evil race, and capable of change, but in them it is so long-term ingrained and reinforced by higher consciousnesses, as to be almost genetic at this point... but it's possible, at least.
So, it's feasible that Astarion may (May; we can't confirm or deny) now be *capable* of change in a way that he wasn't before... but what he shows us is that, vampire aside, Astarion himself is still a selfish, cruel and destructive person, and seems as though he would be regardless - he earns his evil tag by himself even without the vampire consideration - if he is suddenly capable of feeling things and engaging with emotions that he hasn't actually experienced in 200 years, he appears to have decided to continue to be cruel, selfish and destructive, with no regard for the lives of others. (Plot twist; Astarion is really interested in keeping the tadpole because it's been letting him feel things again, like he hasn't felt for hundreds of years, and he doesn't want to give it up... I... could see Larian attempting to run that line...)
