During the discussion in which Obama lied about the Benghazi attacks, you can distinctly hear one person's clapping above the others. As the camera angle switches to the back of the audience, you can see the person doing the loud, leading applause. That person (in pink) is Michelle Obama.

The debate rules are clear: "All members of the debate audience will be instructed by the moderator before the debate goes on the air and by the moderator after the debate goes on the air not to applaud, speak, or otherwise participate in the debate by any means other than by silent observation, except as provided by the agreed upon rules of the October 16 town hall debate."