My hypothesis is that thus far he's considered poor Alissa to be the most inconsequential thing ever to intrude on his thoughts; and having thought more deeply about what happened with him, Lily, and James when he was a kid, he now decides he ought to her to nip her affections in the bud for clearly stated reasons, rather than letting them fester without suitable closure for, perhaps, an unduly long time as his have. His only closure was that he insulted Lily and felt guilty about it forever (as apparently, from his perspective, this was the only thing standing between him and getting to be with Lily); Alissa's could be the end of school, without the issue ever being directly addressed.

The problem with this hypothesis is that it has Snape thinking that student crushes on teachers are persistent sorts of things, and this isn't typically the case.

Will we get a hint?

Well... we don't have much of a baseline to compare this version of Snape to.

Okay, if no one on LW got Aftermath 2, even after working out that the aftermath was supposed to display a change in Snape, then it was too subtle.

Yes, but what part was the change? That he dislikes student affections? That he tells them about it? That they have affections? That he's previously been taking advantage of students in slashy ways?

If anything, I would've expected it to be him actually taking advantage, if he were taking Harry's advice to... oh. Wait. Maybe he is taking Harry's advice and has started looking for deep instead of pretty?

If so, it was definitely too subtle. ;-)

Given the number of theories so far, I'm surprised no one has suggested this one: Aftermath 2 is in fact meant to demonstrate that Snape's behavior has not changed, by displaying behavior that is entirely typical and expected of him; but now that Harry, Minerva, Dumbledore and the readers are all primed to look for changes, they will find them even where they shouldn't.

Whatever it is, it must have something to do with this:

I begin to find your stares disturbing

Hrm... So far best I can come up with are two possibilities, one more charitable and one less charitable toward Snape:

First: From his conversation with Harry, he perhaps concludes that making one's feelings (or lack theirof) to someone that may have feelings for you absolutely clear rather than leaving it ambiguous may be a good idea. (ie, in his own way, he wanted to protect his student from ending up in a situation similar to himself)

Second: He was sufficiently POed at Harry that he's no longer keeping his agreement to not legilimens the students.

I'm not really assigning all that high credence to either of those hypotheses, but they're more or less all I could come up with so far. So... give us a hint? :)

He may have had his mental discipline upset by the events of the previous chapter, causing him to be less in control of his Legilimency in some fashion. I did note the significance of the command to "restrain your eyes henceforth".

But yeah, even if I'm on the right track I don't feel confident of it. Too subtle for this reader.

Harry told Snape that Lily only liked James because of his money and looks. So is it that Snape now thinks his students only like him because of his position and power, whereas before he thought they liked him for who he was? Has he become even more cynical? More inclined to reject people?

ETA: Some reviewers thought it was a reference to Snape performing Legilimency, but of course it doesn't take a mind reader to notice a dreamy-eyed girl.

I actually took it for Snape venting and doing a little dogkicking; so yes, I guess it was too subtle. (It seemed too abrupt and cruel to reflect any good change in Snape.)

Analysis of Harry's conversation with Snape in ch. 27.

"If he were a friend," Harry said, "all the more reason to forgive him."

Possible Snape thoughts: "He implies that I wasn't even a friend of She. How dare he!?" ... consideration of different ways of mutilation ... then "Oh! He can't possibly be like his mother. She had a very high standards for Her friends. Maybe his stepparents taught him this indiscrimination of friends."

"She was shallow"

"SHE was shallow!? ... But She married that brat Potter. Was Her standards high after all? Maybe not. And I gave all the power I could have for her..."

So I think Snape became misogynous. Thus Alissa's affection became irritating for him. I don't know what implications it will have for storyline however.

Edit: Analysis is done by Type 1 processing with Type 2 postselection, so no justification is given. :)

Edit: This hypothesis seems to be insufficient for explanation of emphasis on "wrong" in Aftermath 2, maybe there's something more.

Edit:

1. "Wrong" can mean, that she was aware, that Snape isn't kind of person young woman is supposed to crush on. I'm not sure that this is true for Slytherin. Anyway Snape isn't handsome guy, it's not deserve emphasis to hint that.

2. "Wrong" can mean, that she feels it's bad for her to show affection now. Fits my hypothesis, but not wording "There was probably something really wrong with her...", which imply that she knew it all the way.

Some part of puzzle seems to be missing.

Hm, he did take sexual advantage of the student and then, being far above the 11-year-old-Draco-Malfoy lower bound on villain cunning, altered her memory?

I don't know about subtle. I noticed it on my second read.

Why call it Aftermath 2? Why not just a nameless block? How is it the result of anything?

I guess I didn't fail to notice my confusion.

Dumbledore messed with the girl's mind to test if Snape was still in love with Lilly.

What I'm a bit uncertain about is the 'Ever since the start of this year' part. Has he been setting something like this up every year to have something ready when needed? More like, was that an intended implication?

Mind, the second part only occured to me after I read the reviews re Ch29 Notes.

My interpretation was that he gets a kick out of giving students love potions, reading their minds for kinky thoughts, and then refusing them in a humiliating way. It's a sort of safe sex. Obviously, this is not what you had in mind, as this has nothing to do with changing.

Given that it was called 'Aftermath', I knew it signified some change, but in what direction I don't know. My best guess is that he's not romanticising crushes anymore. So in other words, this is actually a positive change for him.

My actual interpretation was that he'd let his shields down enough that someone could find him attractive.