What turned Snape (Was: JKR site update SPOILERS)

[pippin_999]

No: HPFGUIDX 158922

   
> > Neri:
> > Are you saying you don't think Snape owed a life debt to James at all?
> > Or that he did, but that this wasn't the reason he "turned"?
> > 
> 
> Hickengruendler:
> 
> The later. I think if the Life Debt was the reason, why Snape turned, 
> there would be no reason to make a secret out of it. I think Dumbledore 
> would have told Harry and JKR would have told us.

Pippin:
Um, but Dumbledore did tell Harry, though Harry was not listening
very carefully. Dumbledore  was plain about it: "You have no idea of 
the remorse Professor Snape felt when he realized how Lord 
Voldemort interpreted the prophecy, Harry. I believe it to be the 
greatest regret of his life and the reason that he returned--" 

If we believe Draco's conversion, then we must believe that
a wizard may be consumed by hate, offer loyalty to Voldemort, 
and yet  reject the role of murderer once the reality of the crime is 
brought home to him. 

What is left unknown then is not why Snape turned but what 
convinced Dumbledore of his sincerity. That might have something to 
do with Lily, though I doubt it. The  Lily mystery is why Voldemort 
offered to spare her, giving her the choice which is what made her 
sacrifice so powerful. Maybe Snape was in love with her and  bargained
with Voldemort for her life, but since it is a mystery, Snape is
probably red herring through and through.

Pippin