Burr is usually very friendly and energetic when speaking to friends, or people he feels secure with. With most strangers though, he speaks in a very soft tone when he actually says things. He also is far too polite when he is talking to people he feels insecure talking to. You can usually tell when Burr ISN'T feeling very happy [frightened/saddened/angered] conversing if he's being the most well-mannered guy you'd ever met. But when he isn't skittish, he's just that guy who doesn't know how to zip his trap shut.
But yeah, most of any conversation is situational. Everything depends on the parties involved.