Whoah whoah whoah... a Presta valve isn't supposed to be hissing and losing air as the pump hose is removed from it? ...As long as the pump head isn't stuck in so deeply that the valve head is being depressed while the head is engaged?

I never knew that. I thought it was all just about the weight/slimness of it, or something.

I'm gonna start trying to see if I can inflate mine without putting the pump head in so deeply!