Thanks everyone for the feedback, again. I'm still tinkering with this in the back of my mind. The scene that follows will be up for critique soon, if any of you are interested.
@Aaron DC It's up in the Workshop. The scene that this excerpt is from is part 2 of 3, there's links.
First of all, I think you must realize that the opinions of a few don't represent the world as a whole. Some time back I had to get that straight in my head also. Second, facial expressions do the trick for me. In my family saga, I have two sophisticated friends who go back and forth. One is a smart-butt. The other, classy, well-mannered. Of course, the smart-butt is a little jealous of the high-class one. The smart-butt ask insulting questions enough for the reader not to like her. That's until, once things cool down and get serious, the reader realizes she's of value to the high-society snob. So, in short, I think it's the language they speak that conveys the image of bantering or die-hard seriousness. Don't forget to add a touch of body language. But don't force it. Readers will need an image of what their faces expose. A sly grin. A wink. A simple Humph!