There is unfortunately no way to stop people from writing whatever they want, on whatever language they want. All we can do is give warnings or bans, once we see someone is using a language not permitted. There's also no way to be in every city and in every discussion watching over what players write, so we depend on other players here. If you see someone using a wrong language or inappropriate comments, please report it to game support.
'2.2. Using a different language, other than the relevant server language or English in IGMs (in-game messages), chat messages, in the world chat and in player profiles is not permitted. The server language is determined by the country flags on the server selection screen. Multiple languages can be server languages.'
This rule 2.2. does not ask for players to keep their private discussions in English (or whatever the server language is), but all public commenting and discussions should be in the server language. International servers (COM) are English only servers, even if the server Flag doesn't make this very clear. In regular COM worlds you can only select English as the game language, which tells what language to use.
What players write to each other, or in association forums is irrelevant. But some of us play this/these servers because they are English speaking only.
Last round there was 4 association playing more or less plain in Turkish. Of those 1 got a ban, but from what I heard because of multi accounts, and not due to language.
I tried to report it once, but it seems the ticket didn’t go through.