If the church is not on fire, you should not be talking.There's more, of course, written by Pat Archibold for National Catholic Register and I encourage you to read it. (Found it via Sr. Lisa Doty whose thoughts on the subject I also encourage you to read.
However, that pretty much says it.
I have to admit that I am guilty of a very lax attitude in this area. Coming up on my 11th birthday as a Catholic this Easter, I have generally had only that "chatty" post-Mass experience. Now I know intellectually that I shouldn't be talking then but it is very easy to forget if the other environment is all you have known.
That's why it is good for me, and doubtless for others, to be reminded. We are in the presence of the King of Heaven. A little reverence is good but I don't think we can show too much. Restraining my tongue until I get out the door is a small gesture to offer but I am going to try (again) to make this my new habit.