Inspired by a conversation I had with William, where he suggested that the fourth wall could be a character in the comic. I wasn't sure how to convey the idea of a talking fourth wall visually, but this is the mechanism William suggested. I think it works pretty well!
I'm still not likely to go that route--my current unofficial rule is that I can break the fourth wall all I want, so long as I don't talk about breaking it--but I do like the construction and may steal it from him for other purposes. We'll see...