I applaud your discretion in matters of enunciation, and wish it were much more common.
Not as far as I know. “Haver” can mean to chatter about something somewhat to excess- “oh, he was havering on about xyz”, and it can often mean to talk nonsense. My sister-in-law from the East of Scotland (although further north than the home of the Porclaimers) can say “Oh, Havers!” meaning"Oh, you are talking nonsense".
Returning you to your scheduled thread. 
( I like apostrophes in their proper places: this is a Pet Peeve and I feed it well.)
:smack: …My goodness ppl… Why don’t you get your own “apostrophe thread” or whatever… I think all this talk has well become by either accident or intentionally a major hijack on the Original topic… in fact I’m left wondering, why this one hasn’t ended yet? The OPer has seemed quite content with all the answers they already received and has yet to provide any additional questions…
Well, I thought the topic had exhausted itself and I was going to let it die a natural death, but then, ten hours later, someone decided to post and keep it open longer.
Apostrophe threads never die - they just slowly contract.
Perhaps it’s just the people around me who react to nonstandard usages as threats to the language itself - you’ve never heard the histrionic complaint that the English language (along with everything else in the modern world) is going to hell in a handbasket because no one speaks it right anymore?
My fourth grade teacher actually didn’t harp on us much about grammar as far as I remember; he was a drunk and he wore far too much cologne. But at other points in my education, teachers claimed frequently that certain usages were “incorrect” in some way - that “ain’t” isn’t a word, for example. And claims like these are simply not valid. There is no way to define the category of “words” so as to exclude “ain’t” and include the words we favor. Adeptness at standard English is a very worthwhile goal, but it shouldn’t come along with a condemnation of the child’s native dialect, whatever it might be.
I don’t know, either, why you claim that the “value of skill in the use of language” is “upheld in essentially every human society of which we have record”. Many societies never had and don’t have authorities who busy themselves with telling the population how to speak. I’m not claiming it’s a rare phenomenon, but it’s not universal either. And in many societies, the distinction between “common” speech and the speech of the nobility was carefully maintained - Classical Latin as taught to Roman schoolchildren may well not have been an entirely natural language in the first place, and it was taught to the nobles for hundreds of years after the majority of the population forgot it. “Received English” is a similarly artificial dialect - there is no place in the world where it is a native tongue; it was for hundreds of years laboriously taught to students at British universities for the sake of forcing a distinction between upper-class and common speech.
Historically, at least, the use of standardized dialects has been a major weapon in the stratification of society and the casting of the poor as inferior to the rich. While I support the goal of educating children in a standardized English (for the sake of their own futures, at least), I wish this weapon could be taken away and that children could cheerfully be taught that “ain’t” is perfectly fine in most contexts.
I would consider formal, standardized English to be something of an equivalent to a business suit. A nice business suit is an asset to most people, and it’s required in many areas of the professional world. But there’s many other places where it’s inappropriate, and you won’t win any friends wearing one to the beach. It’s a useful tool in its place, but there’s nothing about it that makes it inherently better than a pair of jeans and a hoodie.
If teachers of language (along with those of other subjects) are to have any success at all, they need to have a clear notion of what to teach. So it isn’t surprising that at any given moment certain things are praised and others frowned on. Some, as you point out, can get a bit too excited about the matter, but the flow of language often passes them by.
I don’t see that a society’s valuing the use of language requires an official authority that tells people how to use it. What I’m saying is that all societies have valued their great orators and storytellers. No authority is needed to determine that the Aeneid is a compelling tale, told with far from ordinary skill - ordinary human nature is enough.
It is obviously true that even those who are masters of formal, standardized English don’t always use it - most are fully capable of speaking informally, as circumstances often demand. Likewise, people who own business suits don’t wear them all the time (and almost never on the beach).
OTOH, the inability to wear a business suit can be a handicap. The inability to speak and write clearly may well be a greater one. When fourth-graders study English, I doubt anyone is so naive as to believe they will in consequence never speak in the vernacular. Rather, the hope is to give them a tool that many in the past have occasionally found quite useful.