Your analysis fucked me up when you pointed out that the Malfoys would have to be very close to Severus so Narcissa would know his address so easily. Just imagining those stuck-up, rich, privileged pureblood wizards going multiple times to a poor neighborhood in the muggle world, to visit Severus... And he had to betray them for the greater good. Like, holy shit, I didn't give this detail the attention it deserves.
And it's so uncommon too. Usually when a character switches sides, it's because the bad guys were never "good friends", and the heroes show what it means to have a good friendship. But not this time. With Severus, all the heroes are awful to him, and the villains (Narcissa and Lucius, at least) treat him well. That's devastating. I'm gonna cry.
I think that if Rowling weren’t simpler than a bread recipe, and if she’d actually wanted to do something ethically and morally complex and interesting in her books, she would have explored aspects like these which, to me, are ten thousand times more interesting than the story of any hero who swears his life to the cause of Good. People are complicated, and the decisions we make are usually based, unconsciously, on emotional impulses, no matter how rationalised we believe them to be. Emotional bonds are extremely important in political decisions.
The fact that Severus had a childhood bond with Lily (and these are among the most powerful bonds in our lives, because they take us back to a crucial developmental stage) and that he felt guilt over her fate is what makes him change sides, because he wants to atone for his guilt. But the reality is that, on that other side, were his abusers, people who mistreated him before he ever became a Death Eater, or who looked the other way while he was being abused. People who, years later, were still making excuses for the abuse they committed and who never showed any remorse.
Meanwhile, on the side of “the bad guys”, there were people who never caused him any trouble and who, as far as we know, neither harmed nor wronged him. In fact, I genuinely believe he had a good relationship with the Malfoys (Lucius was always promoting him and singing his praises for no real reason, and then there’s the fact that Narcissa knew how to get to his house without hesitation). So Severus actually sacrificed his relationships and his emotional bonds with people who helped him survive abuse, in order to help people who had abused him, because that was supposedly in the name of the common good.
And then people have the audacity to say that he was a bad person, a coward, an incel, an obsessive, or that he did nothing good and was never redeemed. Not redeemed? Most of his haters wouldn’t last even half a day in his skin.
