I've seen this a few times. Instead of just being funny or cocky, some guys try to do the whole 'broody' and 'deep sophisticated guy' stuff. It works sometimes.. maybe after you have some level of emotional connection. Also it could be good to do very slightly (like you slip into a deep convo for 1-2 minutes then switch back).

But don't make it your whole schtick. I've seen it from afar and it is not attractive at all. Especially if it's a girl you just met or the 1st date. I've learned this the hard way. Don't open up to a girl you just met... you don't know her enough to be vulnerable. Let her earn your vulnerability, until then... be the rock.