Just to be sure, can you check if this happens in places where ChatJax++ is supposed to work without modification? It would be very strange if it didn't, but I still think it's worth checking.
This message, even viewed in a transcript, will render if ChatJax++ is working properly. Navigating to that page and checking if it does, and what the console says, should be sufficient to check if this modified version of ChatJax++ will render it.