I don't know the exact problem now:
First: Of course I understand the rule because we need one language for "official" stuff to communicate.
Second: I understand that English native speakers think it is very rude to use another language.
But:
What the heck is the problem guys? Do you really have to know everything players are talking? Do you really want to know? Just because they are on the same spot? I have no problem, I know the sentence "i don't speak spanish" in spanish, lol that helps me much, believe it or not.
There are many players who wanna try this game but can't really because they don't speak english.
One night a spanish noob started talking to me. well ok... He knew no english so I used the great google translator

and ran around tmw with him to find anyone speaking spanish to help him. I found some who were speaking spanish in public (omg ... send them to hell!)
Other example. My brother wanted to try this game. He can't speak any English at all because he never learned it. I can't be online the whole time to translate so he decided not to play this.
I myself often speak german to someone, so what? I will not stop that. Sometimes I make fun of someone and use red letters saying "English in public" (btw yes this is making fun of the many many announcements). Or I make fun of languages by trying to immitate them. But I'm not really affected by someone around me using another language.
So why is this a rule and not just a comment somewhere? A comment like "please speak English in public because that's our official language". Just not as a rule. Because in my humble opinion it's no very good rule. Too many people just can't communicate in English.
cu ingame
Leela (Ego nemus sum

)