OoP - Responses to the Evil!Occlumens Snape theory

[Tom Wall]

No: HPFGUIDX 66956

Someone wrote:
* Snape is smarter than that. He wouldn't do the opposite of what 
was necessary, knowing that know-it-all Granger would figure it out.

Darrin replied:
Excellent point. My answer would be that Snape would simply blame 
Harry and in his plea to Dumbledore, say, "Look, he never pays 
attention to me, and he's doing it all wrong, and I resent, 
headmaster, you taking the word of a student, however talented she 
may allegedly be, over mine."

Tom suggests:
Ahhh, but we now know that Dumbledore is a sufficiently accomplished 
Legilimens... so the question you have to ask in order for this to 
be cogent is: "Could Snape (a `superb Occlumens,' in Lupin's words) 
fool Dumbledore?" 

My answer to this, based on what we see of the scope of Dumbledore's 
power in this book, is `probably not.' I know Snape is powerful, but 
he's peanuts next to Dumbledore.

And after all, this new power that Dumbledore, Snape, and Voldemort 
possess changes things considerably. We're going to have to do a lot 
of rethinking. Now, for instance, we know why Snape always knew that 
Harry was lying when he was lying... it wasn't just evil, 
meaningless suspicion. Perhaps this is why Dumbledore was surveying 
Harry so closely after he lied about hearing the voices in CoS. Or 
why he surveyed Snape so closely following the episode in the 
Shrieking Shack in PoA.

It is quite possible (though totally off-canon, but since we're 
dealing with theories anyways...) that in order for Dumbledore to 
fully trust Snape, good old Severus might have had to open up his 
mind to the Headmaster at one point or another. That could explain 
why Dumbledore trusts him so implicitly.

And on a more practical note, Ron thought that Snape was opening up 
Harry's mind, too, and Ron's predictions are almost never correct, 
unless he's joking.

-Tom