Here's Jerry Markbreit's explanation:
"
Twice during the Pittsburgh-Baltimore game, there was a taunting foul called against the offense after the play was over. I'm not familiar with the first one, but the second one was called on the QB for throwing the ball at the defender after being sacked. It was a 15-yard penalty, but they replayed third down. The radio announcers were confused, as was I. Can you shed some light onto the situation? --Chris Mrstik, Alexandria, Va.
The taunting foul to which you refer in the Monday night game was properly enforced. The quarterback was sacked and then threw the ball at a defender. This penalty is part of the play, even though the whistle had blown; and is penalized the same as any other penalty during play. They replayed the down after the enforcement, and it remained third down. The down would not have been replayed had there been a long delay between the end of the play and the foul."
Here's his Q & A column:
http://chicagosports.com/bears/content/story/0,1984,170451,00.html
Bob