I'm afraid your own perspective might be messing with you here. You're an ISTP, which means that you have a tertiary Ni function. ISTJs are Ne-inferior, which means if they use abstract language, it's Ne rather than Ni. Snape doesn't show an inkling of Ne. Ne looks more like this:
I automatically turned and observed Asahina Mikuru: she has a small body and a face that could
easily be mistaken for an elementary school student. Her brown hair is slightly curly, hanging
over her back. Her pair of large puppy dog eyes give out a "please protect me" aura. Her halfopened
lips reveal a row of white ivory-like teeth that, coupled with her small face, create a
perfect combination. If she were given a magic wand with a shiny jewel, she might even
transform into a little fairy!