I've never observed what you suggest. While there are plenty of Westerners who live in Asia a long time and never acquire really good language skills, I've never seen anyone attempt to/inadvertently become less native-sounding. I can't conceive of anyone who has bothered to learn a language well finding it distasteful to speak it like a local. Sure, I have been known to deliberately use the wrong level of respect to either make a joke or to piss someone off, and know I can get away with it, but this is on certain occasions. After 5 years in Asia and speaking pretty good Chinese and Japanese, I would never try to sound ress rike a neichibu supi-ka-.
4 years 8 months ago
I lived in southern Thailand for 10 years but I don't think I could ever get out of my central Thai when I spoke, although understanding the quicker spoken Thai of the south became easier.
4 years 6 months ago
Some of these issues can equally apply in one's own native language. When I go and visit my relatives near the country NSW town where I was brought up I become very aware of how different my accent has become after 3 decades in "the city" and how I express things. I find myself adjusting my accent to sound more "native". Which is the "correct" Australian native accent that foreigners should adopt?