As an English language teacher, I take an active stand against standard pronunciation. Things are much more interesting –not just charming– with the regional variety. In fact, I highly discourage my students who, in misguided attempts at conforming, try to lose or disguise their accents.

Furthermore, any attempt at artificial standardization is not only likely to fail, but also result in the silliness that all too often afflicts grammar classrooms today as a result of the last attempt to standardize the language, e.g. the myth of split infinitives as poor grammar.

It is much better just to allow these things to evolve naturally, as the Great Vowel Shift did, and sit back and enjoy the spectacle.

Impediments to comprehensibility are more likely to arise from intonation and the pronunciation of vowels than from something as trivial as the substitution of /s/ for /z/.

Regional and national variations in accent present no problem in comprehension and often add charm to spoken expression.

My contention is that English has conventions of spelling and pronunciation which can reasonably be taught to all the children in our public schools and mastered by them.

A state trooper from the deep South should be able to modify his speech and form his words carefully enough to be understood by a motorist for whom English is a second language.

An athlete who in the locker room communicates in slurred utterances understood by his team mates should be able to switch into a more conventional mode of expression when being interviewed for the television audience.

I don’t think that’s being pedantic. I think it’s caring about our language and being considerate of other people who speak it.

It’s probably time for English teachers to take a united stand for a standard pronunciation.

The variations that you list are all minor — it’s hard to imagine that any of them would, in itself, obscure any meaning. I can’t help but think that this is more about pedantry than about communication — international English, if there is such a thing, can accommodate all sorts of much bigger oddities before it becomes unintelligible.