That... sounds like Harry's style. So he'd need to be in the trial when it happens. Then someone storms into the chambers and tells Lucius there's been another attack, and Harry smirks inwardly.

How are the two connected?

Chapter 26, "Noticing Confusion" : Don't know if anyone has pointed this out yet, but Quirrell says, "I...need to go off and set something in motion," before apparently going off to accost Rita Skeeter. During their conversation (Ch 25) she thinks about the alleged fact that a tipster directed her to Mary's Room, where she will shortly die. Now she may have thought this before meeting Quirrell -- she definitely had somewhere to be -- but then why would he bother to speak with her?

I just looked at the passage again, and it seems worse than that. She actually thinks,

And his hair was already falling out? Couldn't he afford a healer?

No, that wasn't important, she had a time and a place and a beetle to be.

Snape's plotting here is interesting, but I'm not sure what he is actually trying to accomplish.

Quick rundown of what we know:

1. Snape was the one who sent Hermione the notes on where to find bullies.
2. Snape destroyed those notes when asked to look for them.
3. He went through great efforts to obliviate everyone at SPHEW's final battle.
4. Snape had a conversation with Quirrel where he had his ass handed to him. (either he was stupid when dealing with Quirrel, or wanted Quirrel to think he was stupid)
5. He is probably working outside of Dumbledore's ordersl, and is definitely hiding things from Dumbledore.
6. After the SPHEW girls kept on winning he stopped the Slytherin bullies from advancing any farther.

So I suspect a few things:

1. Snape was the one who was forcing the repeated escalation of the SPHEW situation
2. Snape is actually working to help Harry somehow. (Because of his love for Lily)
3. Snape is not nearly so biased against muggleborns as he pretends to be. (Remember Lily was a muggleborn)
4. Snape is trying to restore the reputation of Slytherin house in much the same way as Harry. (He's cutting down on bullying and is, in a way consistant with his character, making the hatred of muggleborns look stupid)

Now, if we ascribe his love for Lily as his primary motivation (Which "Sunk Costs" seems to support) , his support of Hermione, and his plotting to restore the reputation of Slytherin makes sense. What I don't understand is why he needs to hide this from Dumbledore. Even if his motivations are counter to those of Dumbledore (I.E. He's actually evil), all of these actions would cement Dumbledore's trust in him. I can think of a few possible reasons:

1. Dumbledore thinks Hogwarts needs an evil racist Slytherin.
2. Dumbledore is a control freak and any plots that are not his are to be distrusted. (Seriously, this is Hogwarts, ancestral home of the gambit pileup)
3. Dumbledore doesn't have the best interests of Hogwarts in mind.
4. Dumbledore would think that Snape's methods (Making Slytherin look stupid in its current form, and hurting little girls in the process) are wrong.
5. Dumbledore is insane. (Like a pie)

None of these are particularly satisfying or convincing, hence why i'm throwing the question out there.

Edit: People have repeatedly pointed out that Snape's attachment to Lily was either broken or reduced by Harry's analysis of the situation, and that Snape's kiss in Sunk Costs was a reflection of that, and I can't help but agree.

I'd prefer the BDSM stuff than this. His conspiracy ideals are dubious.

"Keep it secret" just will not work this way.

He tried that, a while back. Ontological loops just give him "DO NOT MESS WITH TIME."

Or, if kept at a reasonable scale, fun with pies and bullies?

I'm entirely familiar with the earlier experiments with time and maintain what I said in the grandparent. See the discussion from back then if necessary. The only reasons that Harry doesn't use his time turner carefully, for practical benefit, are narrative convenience and an irrational protagonist. Much the same as in just about any fantasy fiction.

I am overwhelmingly unimpressed with Harry as a rationalist avatar most of the time. To the extent that I'd call "Methods of Rationality" something of a misnomer. He's reasonably clever and flamboyant but his strategic thinking is abysmal.

(I am Kevin.)