I am enjoying this discussion, though feeling slightly guilty about hijacking the thread.
whs, I feel that when speaking or writing you must know your audience. In other forums that I have been on, everyone is in the US so I know that I can use American slang and colloquialisms. Here on this forum we have such a wonderful international audience -- which I really like. Knowing that is my audience, I try to avoid using too much "American". I also check a poster's Location in their profile whenever possible. Even the use of British English versus American English is something I try to work on. I believe that in most countries where English is used as a second language British English is more common.
For those who are non-native English speakers I am always respectful. They speak at least 2 languages and I don't. Also, I am more forgiving of their English language errors. Those of us in the US and UK have less of an excuse for improper use of English.