In a comment on yesterday's "Mele Kalikimaka" post, Eric asked:
When is a foreign sound so alien to a language that it's "disallowed"? When does a linguist–or just a transcriptionist–decide to throw her hands up and say: "these people will never get this"?
I apologize for misleading Eric by using the word "disallowed", which he seems to have taken to mean that some authorities — linguists or "transcriptionists" — have made a conscious decision to ban certain sound-patterns, or at least to stop trying to get people to say them "correctly". And I also need to make it clear that this has no necessary connection to what people can or can't "get".