English is a rather unusual language that the meaning is mostly carried only by consonants, while vowels are almost meaningless.
What actors seem to be doing is that they focus too much on their accent, and the vowels that define it, and mostly ignore the consonants. Which means you can only hear the accents, but not what is being said.
Sorry but this sounds like nonsense. Vowel distinctions absolutely matter in English. Think of how many words would be indistinguishable otherwise: bout, bought, bet, bat, bit, beet, boot, boat, bite, but, and bait are all distinguished from each other only by a vowel.
(And, yes, these all sound quite different to me, an American, though non-native speakers often have trouble making or recognizing some of the distinctions. Some native speakers further distinguish “bot” from “bought”, but I don’t.)
No. Have you tried understanding someone who can only pronounce consonants but also whose dialect is foreign? It's unintelligible. Vowels absolutely serve a purpose. You're just used to hearing your own words spoken back to you in the same way you've always expected them.
Generally this is in English's favor, I pronounce button differently than my NZ friends, but they still understand me.
English has 5, and no real consensus on how they are used, let alone the tone of voice that you need to use to indicate a specific word.
In tonal languages a rising vowel note is different than a falling, rising and then falling, falling then rising, flat or tumbling tone. The closest English has is the rising tone one makes when asking a question, but that doesn't change the meaning of the words entirely, just the context.
Again, we are not talking about “letters” or the writing system here. Yes, there are many distinct vowels that are written the same, and conversely many different ways of writing the same vowel, but that’s irrelevant to the discussion of spoken language.
And, yes, I know what a tonal language is, and you’re right that English isn’t one. It’s hardly unique or special in that. Most languages aren’t tonal.
My previous example of how to pronounce 'button' varies depending upon where you're from...but is still recognized by the most English speakers. Some folks pronounce it but-ton, others but'n.
Water can be pronounce in a variety of ways. Actually the list is endless...I'm surprised you're arguing the opposite. Compared to Spanish, or any number of languages where the vowels are very specific (disregarding the Castilian ascent), English is very forgiving. Bringing up Khmer's letters was to show that the vowel sounds have been formalized in that language, where English allows for much more variance.
Listen to any non-native English speaker, they can be all over the place and still understood.
This is a distinction in consonants! Different realizations of the /t/ phoneme. The whole claim that started this thread was that English expresses information almost exclusively in consonants, not vowels. Your example directly contradicts that very claim.
Anyway, English is _far_ from the only language where different dialects have a different set of vowels. Quebec French for example has completely different ones from French French.