It may be this or that, but it has to have a purpose.
What's that?
The creator (author) wants to convey a specific meaning by "the writing on the wall".
In other words, that is to distinguish 'the writing' from other commonly and readily interpreted terms.
In this case other interpretation like princet or Prince's St or princest (sic) etc. are to be specifically kept at bay, by way of interjecting this symbol.

That's it; the communication, so what if it is in English.