I think we pull through the title from the data source (TMDB or TVDB), so if it’s numbers it should stay numbers. I’m guessing you’re meaning source in a different way.
Also, TMDB uses episode numbers when there isn’t an official English title.
I think the reason why we require English is because the accents and different characters can throw things off. If we took any language, we could end up with Greek or Arabic or Japanese characters. Also, since the developers primary language is English, it’s a way to monitor data and make sure its user friendly.
There are hopes to be translated into multiple languages one day.