I don't think I've ever done it before, because in a series where characters sometimes break the Fourth Wall, it can easily be misinterpreted as addressing the reader (which I have done). What I usually do instead is include the top or side of the P.O.V. character's head to reinforce it, but that didn't really get the feeling of being cornered that I thought was necessary to explain V's reaction. I just took a chance that the current serious subject matter would cause the reader to instinctively discount the idea of a meta-gag.