I don't understand what you want to tell us:
1.) Should people (including Americans) make a language skill test before using the board or becoming a moderator? The most misunderstandings happen between the users on the board (and are not due to moderating a thread) and many of them speak English as their native language.
2.) Does is mean that there are no mistakable statements if there are only moderators who passed a test as described in a)? Oh no! Misunderstandings happen always No matter how fluent people speak a language.