Deep south here, and I was raised with the principle that if it's worth saying, it's worth saying succinctly. Mindless yabber still gets me 12 shades of hostile.
What if the person really friendly and upbeat, and what they're saying is really witty and intelligent?
It's not all mindless. Usually it's pretty sharp.
I mean, you have to really keep up with the conversation and respond to sudden shifts.
Soz, you will totally get this....
You're talking in a public place, a restaurant, and all of a sudden someone really slutty looking walks in. You say to your friend, without missing a beat, "Oh Christ, look at THAT one" really quiet voice and a flicked eyebrow in that direction. Then you go immediately back to the conversation.