Pensieves and other magic (wasRe: HBP (Snape's) old school textbook:

[spotsgal]

No: HPFGUIDX 137060

> Alla:
> Oh, but Potioncat, don't you remember that person can modify his 
> own memory before putting it in the pensieve? :-) 

Christina:

It's easy to tell when Slughorn's memory was modified because Harry is
surrounded by a "dense fog" and the scenes fades away, only to come
back again.  None of this happens when Harry is in Snape's memory.

Also, I find it difficult to believe that Snape's pensieve memory is
incorrect just because of Lupin and Sirius's reactions to Harry
telling them about it.

(OotP, US, page 670)
"Yeah," said Harry, "but he just attacked Snape **for no good
reason**, just because - well, just because you said you were bored,"
he finished with a slightly apologetic note in his voice.
"I'm not proud of it," said Sirius quickly.
[...and a little later...]
"Did I ever tell you to lay off Snape?" he said.  "Did I ever have the
guts to tell you I thought you were out of order?"
"Yeah, well," said Sirius, "you made us feel ashamed of ourselves
sometimes...That was something..."
[...down some more...]
"She started going out with him in seventh year," said Lupin.
"Once James had deflated his head a bit," said Sirius.
"And stopped hexing people **just for the fun of it**," said Lupin.
(end quote- all emphasis mine)

If the Sirius and James felt "ashamed of ourselves" for their actions,
they knew they were in the wrong.  You don't feel shame for actions
that have ample justification.  Note that Harry specifically mentions
that James and Sirius started the OWL incident without provocation
from Snape, and not only do Lupin and Sirius refrain from making any
sort of correction, Sirius even says that he's not proud of what he
did.  When talking about the prank in PoA (which IMO is a much more
dangerous incident), Sirius says, "it served him right," but for this,
Sirius just tries to explain why James and Snape disliked each other
in the first place (putting the blame on both sides).  If James was
more injured that the pensieve memory showed, why didn't Sirius or
Lupin make some kind of comment like, "Yeah, we hung him in the air,
but you should have seen Snape attack James- he was gushing blood
everywhere!  So whatever we did to him was just."

I have no doubt that Snape got his jabs in where he could and was
probably pretty vicious, but I also see no reason to believe that his
pensieve memory is wrong.


> Alla:
> Besides, Dumbledore stresses that Slugghorn did a poor job out of 
> modifying  his memory. It suggest to me that people could do a 
> better job out of it.
> 
> And we all know that Snape is a powerful wizard. :-)

Christina:

Yes, Dumbledore does say that Slughorn's tampering was "very crudely
done," *but* he says on the very next page that "Professor Slughorn is
an extremely able wizard..."  So either Slughorn very hurredly
tampered with the memory, or there isn't a way to tamper with a memory
completely undetected (some traces of the tampering remain).
 
> Alla: 
> Oh, did I tell you that now I am almost convinced that Snape 
> indeed left Pensieve on the table for Harry to see?
> 
> Potioncat:
> But to what point? And how was he to know they would be interrupted? 
>
> Alla:
> I am sorry, could you clarify? What do you mean " to what point"? To 
> what point in the memory Snape wanted Harry to be a witness to? 

Christina:

I could be wrong here, but I think Potioncat is trying to say, why
would Snape want Harry to see that particular memory?  What would be
the point of showing him?  Harry already hates Snape- showing him what
could be viewed as a sympathetic memory is *not* going to change
Harry's mind about Snape.  Why would Snape was to change Harry's
perceptions of him anyway?  You could say that Snape just wants Harry
to realize what a prat his dad was, but I find it really OOC for Snape
to use a completely humiliating memory to prove that point.  Snape
pulls Harry out of the memory just as things start to get *really*
humiliating.  There's no way he could have planned his exit and
re-entrance of the room in order to ensure that Harry would be
interrupted right at the worst part.  Also, I would think that if
Snape just wanted to say "I told you so" to Harry (concerning James),
he would have continued giving Harry Occlumency lessions just to gloat
at him.  If Snape really planted the memory for Harry to see, he would
have followed it up with endless jabs- "See Potter, what do you think
of old Dad now? *smirk* *sneer* *gloat*"  We don't see any of this. 
In fact, we see the opposite.  Snape throws Harry (*literally*) out of
his office and refuses to give him additional lessons.  He goes
against Dumbledore's specific orders to teach Harry, and he *never*
brings up the pensieve memory again.  Snape is so angry that one of
his jars explodes.  Compare this to Harry's detention in HBP, where
Snape purposefully tries to get Harry to see how bad James was.  The
files have nothing to do with Snape (or anything that could embarrass
him), and Snape gloats at Harry:

(HBP, US, page 532)
"I thought you could start," said Snape, **a malicious smile on his
lips**, "with boxes one thousand and twelve to one thousand and
fifty-six.  You will find some familiar names in there, which should
add interest to the task..." [...Snape reads a sample card...] Snape
**sneered**.  "It must be such a comfort to think that, though they
are gone, a record of their great achievements remains."
(end quote; again, all emphasis mine)

This is Snape doing things with purpose.  This is Snape in his
element.  Snape exploding jars and physically abusing Harry is not.

Christina