Snape's Worst Memory

[sylviablundell2001]

No: HPFGUIDX 81176

 I would agree with previous posters that Snape probably put this 
memory into the Pensieve in order to clear his own mind of something 
which, for any number of reasons, he didn't want Harry to see. It is 
nowhere mentioned in canon, as far as I can remember, that Snape knew 
that Harry had any knowledge of what a pensieve was, so felt quite 
safe in leaving him alone with it.  When he returns and finds that, 
not only does Harry know exactly what it is, but is actually using it 
and thus witnessing the scene Snape most wants him not to witness, he 
is naturally livid. Is there any authority for believing that Snape 
does know that Harry knows about the Pensieve?
Sylvia (who thinks Snape was perfectly justified in throwing things 
at Harry)