The loop hole - Snape in Dumbeldore's pensive

[literature_Caro]

No: HPFGUIDX 134980

I have wondered why DD gave Harry such a lame answer when being asked
for the reason why DD believes that Snape is loyal in HBP. Now I came
up to something in GOF that makes me believe that DD told Harry what
Voldemort wanted Snape to tell DD to convince him:
In the chapter where Harry breaks into DD pensive in GOF (I think in
English it is called "The Pensive") and sees Karkaroff's trial Snape
is denounced being a Death Eater. There DD says that Snape was indeed
one but started working as a spy before (!) Voldemort fell.
But DD tells Harry in HBP that Snape felt remorse that the Potters
died and joined him which was after (!) Voldemort fell. This leaves
two choices:
1. DD let Snape work for him before he was sure of his loyalty, which
I think far too much unlike DD, or
2. DD did not tell Harry the plain truth because Harry is far to weak
at Occlumency to keep Snape's true identity hidden, or
3. DD cannot tell Harry the true story for this is secured by a secret
keeper (other than DD).

So this could be seen as a real hint that Snape is not evil.

Caro