but if a person has a post history where he only insists to speak in English on a local board, what do the rules of bitcointalk say in this regard?
this will entirely depend on the local board's rule. anyway, I don't know about other local boards, but in the Pilipinas board, users can create threads or reply to someone using English. I guess the fact that English is our second language is probably the reason why it is allowed(not really sure if it is the reason).
That's true I am not offended if one of my countrymen creates a thread or posts in English, my English is not perfect but English is our second language, it's a fact that many of our countrymen prefer to post in English when it comes to local board it's up to the moderator to set up rules and if there is a request from members then it's up to moderators to consult the community or do a poll.
And besides we have hundreds of different dialects and English is one of the languages that binds us besides Tagalog.