I like passionate people who really care. They are careful to explain things. I have rejected candidates because when they talked about their previous projects, they couldn't explain them in terms that a normal person could understand. Often, engineering majors will just assume that everyone knows what Bates Theorem is or what Peano's Axioms are.
If they start doing this, stop them for a minute and say, "could you do me a favor, just for the sake of the exercise, could you please explain this in terms my grandmother could understand." At this point many people will continue to use jargon and will completely fail to make themselves understood. GONG!
Joel On Interviewing 8: Jargon