Whys is Snape allowed to continue spying?

[Hagrid]

No: HPFGUIDX 131484

> > Juli: Actually I always thought that "The one who has
> > left me forever, he'll die" is Karkaroff, "The Coward
> > who'll pay" is Severus, and I agree that Barty of
> > course is the loyal one.
> 
>   Chris: In GoF ... p. 710 Snape: "...This Mark has been growing 
> clearer all year. Karkaroff's too. Why do you think Karkaroff fled 
> tonight? We both felt the Mark burn. We both knew he had returned. 
> Karkaroff fears the Dark Lord's vengeance. He betrayed too many of 
> his fellow Death Eatersto be sure of a welcome back into the fold"
> 
>   Once LV touched the mark, Karkaroff fled ...
>  This to me is the description of a coward, too 
> scared to return. I think Karkaroff was LV's reference to a coward 
> who will be punished.
> 
> >Juli:
> > If Lucius told LV that Snape was a teacher in Hogwarts
> > (and trying to get Harry kicked out), then he must
> > have known that "no-one can disapear from Hogwarts",
> > then of course he couldn't arrive at the Graveyard on
> > time, then after DD told him what to do he could have
> > left Hogwarts and then show himself to LV.
> > 
>   
>   I don't think LV would fall for this excuse. "I'm at 
> Hogwarts...gimme a sec and I'll be right there." Besides, I think 
the 
> information LV has on the Death Eaters is what he has gleaned from 
> speaking to Pettigrew, Bertha's memories, Crouch Jr., and Crouch 
Sr. 
> LV does not see or speak to any DEs until they apparate into the 
> graveyard. So obviously he learned of Snape and Karkaroff from one 
of 
> these sources.
> 
> Chris
> labmystc

aussie:

Once Snape visited LV, he would have been full of his (Snape's) 
version of what happened to Couch Jr after Harry got back to 
Hogwarts. It would have been things that LV didn't know about till 
Snape reported.

Retuning with this ground breaking news would have helped Snape's 
standing with LV.

He wouldn't have told them everything as it happened. But his 
version would have to explain reports from students still outside at 
the Quidditch field when Snape went with DD to see "Moody" and took 
time in the hospital. 

He probably wasn't aware of LV plan with "Moody" so could say he 
continued "pretending" to support DD to stay close to LV's enemy 
until it was too late to save Couch Jr. He then stayed for long 
enough to work out how Harry escaped again, and DD and Fudge's plans 
after Harry reported to them.

This may have appeased LV enough to allow Snape to remain ... 
although he may have been punished with a Cruciatus Curse to ensure 
his loyalty.

aussie / Hagrid