A few things, first thank you for adding a font selector, it'll makes things a lot easier to read. Second, while on the topic, could you add a 'Hide' button? Desktop users can middle mouse click or press H, but mobile users can't. To add one, add this to line 1437 in screens.rpy:
textbutton _("Hide") action HideInterface()
I'm including some changes you can make to change naff's font, as well as some other changes:
1) Change style prefix of font selector from check to radio 2) Change names of fonts in gui preferences from font_1, font_2 to more descriptive names. Make the same changes in the actions of the font selector. 3) Add 2 fonts to gui.preferences for naff's text and naff's name. 4) Change the gui.button_text_font definition to allow for it's font to be changed too. 4) Add the actions to change these 3 new fonts to the font selector buttons in options. 5) Change naff's character definition from what_font, who_font to what_prefix and who_prefix