Occlumency questions

[dungrollin]

No: HPFGUIDX 114613


I've been reading a load of backposts (though Yahoo!Mort may have 
stubbornly not revealed the most pertinent amongst them) and 
wondering about Snape's Worst Memory and the things he put in the 
pensieve.

The assumption that (after my grossly inadequate search) appears to 
have been made, is that Snape hid those memories because he
didn't want Harry to see them. But could it not also/rather be 
because they were memories he found so emotion-provoking that he 
would not be in a fit state to teach Occlumency with them in his 
head?

This would work with the idea that `The Pantsing' is not
actually Snape's worst memory - there must be plenty of worse
things that have happened to him - the title of that chapter came 
from Harry's assumptions.  `The Pantsing' is then
downgraded to the status of a rage-provoking memory that Snape finds 
difficult to supress, particularly in Harry's presence.

I then wondered whether having some thoughts removed to the pensieve 
may have changed some of Snape's answers to Harry during the 
lessons. These memories are in the pensieve when he tells 
Harry `Yes, that is my job', though not throughout the first
speech of the first lesson.  Could there have been a memory that he
didn't have that would have changed that answer?  Others have
noted that it wouldn't make sense for Snape to imply so directly
that he was spying if he were afraid that You Know Who might be 
hacking Harry's brain (figuratively speaking).

But something else jumped out at me, and I've not found any 
discussion of it – perhaps because everyone was so delighted to
have so much else to analyse in the few pages dedicated to the 
Occlumency lessons – is that Snape glosses over *how* they know
that You Know Who knows that Harry's seeing into his mind.

OotP: Chapter 24, Occlumency. UKHB: 470-471
`How do you know?' said Harry urgently.  `Is this just
Professor Dumbledore guessing, or -?'
`I told you,' said Snape, rigid in his chair, his eyes slits,
`to call me "Sir".'
`Yes, sir,' said Harry impatiently, `but how do you
know-?'
`It is enough that we know,' said Snape repressively.
`The important point is that the Dark Lord is now aware that you
are gaining access to his thoughts and feelings...'

So how *did* they know? Snape (over the course of half a page 
because of Harry's constant interruptions) basically says that it 
was during the snake vs Mr. Weasly vision that You Know Who realised 
that Harry was seeing what was going on.  How did LV know?  And how 
do Snape and the Order know that he knows?

Is it significant that they know that, but not that Harry's
already dreaming about the corridor?  Is Harry's dreaming about
the corridor *up until* snake.vs.Weasly because You Know Who is 
dreaming of getting his hands on the prophecy, but *after* 
snake.vs.Weasly Harry's dreaming because You Know Who is feeding
him misinformation?

Have I just repeated what a load of other people have already said?

Dungrollin, pondering half-formed thoughts...