The only unsavory types of people I encounter in my lecture halls are those who engage the professor in lengthy, abstract, past-current-material, or unclear discussions. They drag on and on and on and on and on about something or other that's related to the subject but only tangentially to the current material. Even worse if they're jumping ahead, because then they're just being pretentious.
They all just come off as pretentious or overly distracted with some tangentially-related topic. God, it'd be nice if we could just cover the material more in class to clarify stuff. Lectures on course material and NOT academic forums people.