You don’t have to take everything so literally, Susan. It probably started out with one person who thought he was being funny (and what can we say, he was right) and it created an endless snowball reaction, because everyone wants to get in on the fun.
We only have one question, or two: why did someone marked an X, and even more baffling, what’s the winky face supposed to mean? Did they or did they not flush? Even when the sign isn’t being passive-aggressive, it doesn’t mean you can’t be!