Edit any page on the Romanian Wikipedia without having syntax highlighting enabled. Enable syntax highlighting and then paste any of the wrong Romanian diacritics: "Ş ş Ţ ţ". Preview or save the page: the characters are saved as they are, because the code that corrects them does not run.

To ensure the code is correct, repeat the steps above without enabling syntax highlighting and/or with syntax highlighting already enabled. In both cases, the diacritics are corrected to "Ș ș Ț ț", as they should. From what I can see the hook is always correctly set, but it gets dropped when enabling syntax highlighting.