I just tried creating a page using a unicode character ("á" or ´), and when I click save I get an error message asking "Are you trying to break something?".

Reproducing this is very simple: create a new page, enter a menu page title with a latin character (e.g., "Página de teste") and it will fail to save. Using the exact same string, but without the accent works (i.e., "Pagina de teste").

Note: this does not affect the "Page title", only the "Menu page title".