:Hello. "Gloss" is a technical term in lignuistics meaning "meaning." If a work of art is primarily known by its foreign name in English then its translation is not exactly a synonym (hence not covered by MOS:BOLDSYN) of the title of the work, it is just a translation. Translations are usually given in quotation marks. Regarding Die Zauberflöte: in practice MOS:FORLANG supercedes WP:R#PLA wikiwide.