Voldie isn't like any other Legilimens in recorded history. He doesn't need to look you in the eyes, and if your shields are that rusty he'd creep in so softly you'd never notice a thing.

Harry and Quirrell spend a lot of time together, and now we learn that he might not even have to look Harry in the eyes. How much of Harry's brain has Quirrell already mapped out? Perhaps this is why he is always playing "one level above you". Maybe this is why Harry doesn't notice some things he otherwise might.

I'm going to start reading all their conversations assuming that Quirrell can read all of Harry's thoughts in real time the same way we can, and interpret all his statements in light of that. Could be interesting.