Anonymous wrote:??? Why on earth would anyone think that's rude? I've conversed with many people who I overhear speaking my language. They're usually not from my home country, but they're from one of our former colonies. DH and I are foreigners here and when we get together with friends from our home country, naturally we speak our native tongue. I've also noticed that Americans who learned our language in school, especially those who then went on to live or work in our home country, love to practice with us.
When I was a foreigner in another country natives would zoom in on me as a target-practice for the language they were learning. Even if they knew I was fluent in their mother tongue. Its rude if it becomes an expectation of 'free' tutoring rather than just something you're comfortable with. Obviously it doesn't bother you - which is good.