I am no chat master, but i do believe that text or open chat members may be able to communicate in different languages - some spellings may be red-worded. The game is designed for primarily engish players, so additional language capabilities probably aren't accounted for.
however, I could be wrong...I don't know everything
Well, I'm brazilian, I had some local friends playing with me as well. In terms of communications we have 3 scenarios:
Text Chat: This needs to happen entirely in english... to be honest someone who has 0 knowledge of english will not find or step into this game. Text Chat does not support any word that's not on dialogue (in terms of other languages). So we must talk with words we know or can easily find. The outcome is pretty awkward for english hearers as my friends would often shout "i don't speak english" then proceed speaking english words in a foreign fashion.
Open Chat: By far the easiest way to talk, Open actually allows you to speak in any language in appropriate characters. Though some foreign words can get in the way of an english filter, simply because parts or mostly abbreviations of the english curse can compose a portion of a casual term in another language.
Swearing Chat: Awhile I came across a brazilian stranger who were working around the filter to curse others in portuguese, a very unpleasant individual... I wondered why he would need to do that being that the filters typically only apply to english terms. I tested typing (never speaking) some into chat and found out they come up red in Open Chat. Meaning despite not covering casual chat, KI is careful enough to block curses in other languages!
KI is very zealous with their chat systems, so I don't think they could ever cover other languages without breaking needed filters on english which is the majority and way more needed (in a family friendly game) than adapting for many languages.