It’s more than a little strange that Tumblr supports (well, “supports”) localization for theme content, but not for any custom variables that you might define. I guess I just have to blindly hope that my theme’s non-English-speaking users can all figure out what “Mobile Styles Everywhere” means, instead of presenting the option text to them in their own respective languages.
I guess those who cannot remember gettext are condemned to reimplement it, poorly.