Why did Snape teach Occlumency?/Snapes Trustworthiness

[potioncat]

No: HPFGUIDX 103616

Neri wrote:
snip
 For example, Harry in PoA is 
> appalled when Lupin drinks the potion Snape made him, and hints 
that 
> Snape "will do everything to get the DADA job". In fact, PoA is 
the 
> book were Snape behaves most horribly out of all the five books, 
but 
> this still didn't make most readers suspect him. 
snip

Potioncat:
Interesting...first Alla, now Neri...

Now "I'm" starting to suspect Snape!

Funny that you mention PoA as Snape's worst.  I know he has that fit 
at the end, but to me he's much worse in GoF. Or perhaps he's at his 
worst from the fit at the end of PoA to the scene at DD's office 
toward the end of GoF.  (where he appears to delay Harry)

Potioncat