Twitchy, prowling Snape?

[Berit Jakobsen]

No: HPFGUIDX 86094

Did anyone else notice how Rowling describes Snape in the pensieve 
scene? OoP p. 566 Bloomsbury:

Quote: "Round-shouldered yet angular, he [Snape] walked in a twitchy 
manner that recalled a spider, and his oily hair was jumping about 
his face."

The twitchy spidery thing really caught my eye. This is not at all 
how Rowling describes Snape's manner of walking as a grown-up. 
Whenever Harry sees him, Snape is either "gliding", or "sweeping", 
or "striding" or "walking swiftly". All these imply someone moving 
elegantly and with ease rather than clumsy or oddly. So why this 
twitchy description in the pensieve scene? What does a twitchy walk 
say about the person in question?

The only other description of Snape's walk that might not fit in with 
the "elegant" is his "prowling" (PS p. 165 Bloomsbury). It says Harry 
recognised his prowling walk in the scene where Snape threatens 
Quirrell in the forest. I don't know if "prowling" goes into 
the "twitchy" category or not :-) But if Harry easily recognised 
Snape's prowling at the time, it follows that Snape usually walks in 
a prowling manner, or Harry would not have recognised him. Does that 
mean Snape usually moves around "striding in a prowling manner"? I'm 
confused .-)

So, what to make of this? Is Snape's walk twitchy, or is it 
sweepingly elegant? It couldn't possibly be both? And what does it 
say about him as a person...?