I was thinking that the sign-reading final boss will be things like arbitrary messages on dot-matrix displays. They frequently use grammatically incorrect phrases, short hands, and abbreviations. And they can have multiple parts of the message cycling on the screen at any given point. For e.g.
View attachment 841966
Even as a human, it takes a lot of contextual knowledge to understand that this means "Exit A75 Westbound is closed every day from November 28 until December 5 from 7 PM to 6 AM."
EDIT: As proof of how much contextual knowledge this takes, I just realized that this image is from Scotland, and so "A75(W)" isn't referring to an exit. It's the name of the highway. So the entire A75 Westbound highway is closed from those dates and times in this context.