There are also sometimes people speaking Russian (the characters they use look like it).
Most likely Cyrillic, a derivative of Latin.
Secondly, I prefer English, as it has mostly become the universal language for us to speak regardless of location. Can't be sure for other, sentient races (that clearly aren't human), can I?
Minetest needs to have an inbuilt system like the current *.po system, but entirely for mods - allowing strings for chat messages, help strings, etc to be localised to the system, but the mod provides it, so other users of different languages can use a localised mod, instead of MinetestForFun, where both English and French are used. French players would be able to recieve French localisation - and English speakers would be able to see a English version of that text. (I'm pretty sure I've seen a server entirely translated into Spanish or something, mod items and nodes included. Something like an API call to handle different languages would be very, very appreciated.)
I'm going to provide a potential system for this.
minetest.string_language({"en_GB", "This is a string in English."}, {"fr", "Ceci est une chaîne en français."})
This is just boilerplate, and could be adopted. If the region language was French, the "fr" table would be returned, instead of the en_GB table.