OK, Lab Rat, I HAVE to ask. You mean to tell me that someone actually did a study where they did brain scans of people while they read text that had two spaces after a period vs. one space? REALLY? Who did this study? Where? When? Please provide proof.

Come on now, poetic examples are pretty much irrelevant to grammar, usage, etc. ee cummings used weird punctuation and capitalization to create various stream-of-consciousness moods. Does that mean that no one should ever use capital letters again?
I think it was Carl Sandberg who wrote a poem arranged on the paper to look like a brick wall. So, now geometry is part of grammar, too?
Lewis Caroll just plain made up, I dunno, a few dozen words in the poem, Jabberwocky. So, now it's standard English to completely make up your own words out of thin air?
William Shakespeare couldn't spell his name the same way twice, even in the same document. "Standard" spelling hardly existed back then.
Great poets and writers are revered because of the ideas, thoughts, and feelings they convey, and the way they convey them, not because they're good grammarians. Many great works, even by expert wordsmiths who delight on turning a phrase just so, are created by throwing the "rule book" out the window, usually, intentionally.
Holding up famous writers, especially poets, as bastions of good grammar just seems to me to be completely misguided.

I'm glad I could help. Thanks for the mention. And thanks for creating a great site!

John, when you say "...but some commentators, who apparently haven't done their research, persist in saying it's wrong...", who exactly are you referring to? Since your last two posts, in well over a year, no one has asserted that "hung" is wrong. Actually, in all of the above posts, only two commentators, the second and third, back in 2005, made such an assertion, and only once each. How exactly does that qualify as "persistence"?

Are you referring to my reply to alla arcuri? I never said that "hung" was wrong. I merely said that if a hanging is self-inflicted instead of capital punishment, then "hanged" is still appropriate. Just how much "research" is required? A simple check of one or a few dictionaries confirms what I said.

You have stated several times (I assume you're the same John as before) that "hung" is correct, but you have never claimed that "hanged" is incorrect, did you? Can I assume you don't have a problem with the word "hanged"? You're not saying "hanged" is wrong, are you?

Every source I have checked says that "hanged" is especially appropriate to describe death by hanging (and no, I did not just say that "hanged" is right and "hung" is wrong). I don't think you disagree with this either, do you? So, um, what's the problem?

Most people don't say they "hanged a picture", right?. And, I guess some newsreporters notwithstanding, most people still say "hanged by the neck until dead", right? And if both these statements are true, that still doesn't mean that "hung" is wrong in the same context, right?

by the way, who won the bet?

Alla, it doesn't matter if the hanging is self-inflicted. "He hanged himself" would still be correct.

Regarding: "...if it's even correct to say such a thing...", Yes, it's perfectly correct to say "I haven't known." It's an example of the present perfect simple tense. Of course, it's the negation.

Regarding: "...if it's possible with that statement to indicate that something was not known at a point in the past, but is known in the present." This isn't the case. Actually, exactly the opposite is true. The present perfect is used to describe things in the past that are still true in the present or may be in the future (or, in the negation, things that were untrue that are still untrue).

If you wanted to indicate that something was true in the past but is no longer true (or the negation, something was not true in the past but is now true), then you would just use the simple past tense.

As Janet already pointed out, your example doesn't work very well. Here, the simple past tense should be used. In the negative, it's "I didn't know." However, using "I hadn't known" would not be correct in this particular example. It has nothing to do being "hypercorrect". "I hadn't known" is the past perfect simple tense. It means that in the past, you did not know, then, at a later time, but still in the past, you did know. For example, a response of "I hadn't known until Bill told me earlier today" would be ok.

Some more examples:

Simple past tense:

"I knew Bill" means in the past I knew Bill, but don't know him any more. maybe we lost touch or he died or something. If I still knew him, I'd just say "I know Bill".

In the negative,

"I didn't know Bill" means the opposite. I didn't know him, but now I do.

Present perfect simple tense:

"I have known Bill for a long time" means I knew him before and I still know him now.

"I haven't known anyone who can make good pizza at home" means I never personally knew anyone who could make good homemade pizza, and still don't know anyone who can.

Also note, the verb "to know" has many different meanings. I'm sure there might be examples, especially colloquial ones, that don't fit these definitions very well.

I think the comments about "try and..." implying success for the action of the second verb may be on the right track, but need some clarification. Completion may be implied, but actual successful completion is not necessary or even likely.

It seems that "try and..." is usually used in the imperative, future tense, or with modals, where the outcome is still indeterminate, but rarely if ever in the past tense or simple present tense.

It should be obvious that in "I will try and stop him", future tense, it is impossible to have already actually "stopped him" in the future.

Only in the past tense would actual success be required, which may explain why you rarely or never hear it.

for example:

"Just try and stop me," I said. So, he tried to stop me.

You wouldn't likely see "so he tried and stopped me," at least, not unless he actually "stopped me". If that was the case, you'd probably just see "so he stopped me".

Similarly, for go and see:

My dad said "Go and see who's at the door" so I went to see who was there

not "...so I went and saw..." Not necessarily incorrect, but I think less likely to be said.

In the imperative, etc., using "and", because of the implied required success may have a sense of determination not present when using "to".

Tolken, I think you're presenting a false dichotomy. Nouns are used as adjectives all the time in English. Adjectival phrases including nouns also modify other nouns. Compound words may be made up of nouns used as adjectives modifying other nouns. They can be both. They're two different paradigms. Something can be both a compound word AND made up of two nouns, one of which is adjectivally modifying the other. While we're at it, Compound nouns don't have to be made up only of nouns. They can be made up of plain old adjectives modifying nouns. There are even compound verb-verb combinations that are nouns.

This should be especially obvious in the examples you gave, as they are all endocentric compounds:

Table tennis, is a kind of miniature tennis that is, uh, played on a table. Football is a game where you kick a ball with your, uh, foot. Toothpaste isn't just any paste. It's a paste that you use to clean your, uh, teeth, yes?

Animal doctor, horse fly, etc. etc.

Uncle Ben, I must disagree with some of your points. Aunt is not the only 'au' word that has an 'a' sound. What about 'laugh'? And how about 'draught,' variation of draft' and pronounced the same, or 'launce', variation of 'lance'?

Also, if aunt were the only word pronounced that way (which it isn't), that still wouldn't really prove anything. I'm pretty sure that 'gauge' is the only word pronounced g-ay-ge, with an 'ay' sound. No other word uses the 'ay' sound for 'au', but no one at all would claim that it's pronounced g-ah-ge or g-aw-ge, right?

Of course, I do agree with your main points: both a-nt and ah-nt are correct pronunciations with a-nt perhaps being somewhat more common, depending on geography. Why something so simple has become such a battle out here is really beyond me.