I think you must educate your readers.
Or… apply something like Detectlanguage.com API in your forum.
Right now, discourse does not use something like that.
May be, if you post this request into Marketplace some semi-god from ruby could apply it.
I’m not sure.
Regards
Ps, others API’s:
http://www.basistech.com/text-analytics/rosette/language-identifier/http://www.lextek.com/langid/https://github.com/shuyo/language-detection/blob/wiki/ProjectHome.mdhttps://cloud.google.com/translate/docs/?csw=1(google translate API docs)