This one is interesting....

When the File Manager "System" List got common file System locations the entries were added as translated strings. For example, IFACE_("Desktop")

But the list structure that those names are added to does its own translations, so translating those strings is redundant. This "double translation" doesn't cause as much of a problem as you'd guess and in almost all cases you wouldn't notice. When "Desktop" is translated to "Escritorio" in Spanish, translating it a second time is non-destructive because when it fails to find a Spanish translation of "Escritorio" it just leaves the word the same.

The only time it screws up is if you start blender in a language other than English, then change the language to something else. At that point you will see incorrect words there until you restart. This is because it can't find a Japanese translation of "Escritorio" - we have translated the msgid which are always from English. The following shows English blender with Spanish System list (until restart):

This patch just removes all the IFACE_()) here and replaces with N_() and everything just works.

Thanks for @Ray Molenkamp (LazyDodo) for tracking down this interesting problem.