On the trivial and the profound.

[pippin_999]

No: HPFGUIDX 165654

> Neri:
> This isn't law. It's magic, and a very dangerous one. Draco doesn't
> fail with the necklace and the poison, because he has not been caught,
> and thus he's still free to make another try. For the same reason, as
> long as Draco hasn't fixed the cabinet but still has a fair chance to
> do so, he hasn't failed yet.

Pippin:
Okay.

Then by your own reasoning, if Dumbledore fakes his death  and
Draco walks free (though hidden by the order), then as far as
 the magic is concerned Draco still has a reasonable chance of killing 
Dumbledore, and Snape should not be felled by the vow. 

No cheating required. 

Also,  if Dumbledore should die of some other cause, then the
magic won't think it's necessary for Draco to kill him, and once again 
Snape will be free of the vow. It's not cheating, it's just taking 
advantage of the rules JKR has shown us.

If Snape knows all this, he should know that he has a reasonable
chance of evading the vow. It's not foolproof, hence the twitch.
But the odds are much better than Bella thinks because

a) she doesn't know the Order has been faking deaths
b) she doesn't know that Dumbledore has undertaken the
highly dangerous task of horcrux removal and may soon be
dead in any case

> Neri:
> In Harry's case we are told what's going on inside his head, so we'd
> know that he has always meant to die himself, not to kill Dumbledore.
> Although even in Harry's case there would always be an ugly suspicion
> that subconsciously Harry has chosen his own life over Dumbledore's,
> say because he was angry with him. This is probably why JKR has never
> made Harry promise such a thing. But with Snape we don't even get to
> look into his head, so we'd never know for certain that he has
> intended to die himself. 
>

Pippin:
We can know  the same way we know that Sirius didn't subconciously
mean to  fail the Potters. He raises that ugly suspicion himself,
"I as good as killed them" but in the end Harry is sure that he
would have died for them if he could. That his  plan ended in
bringing the Potters' doom upon them all the sooner was not 
Sirius's fault but the fault of the traitor.


Pippin