I'm going to try this one more time then I'm out, so I suppose by the rules of this forum, you'll "win," and will merrily go about your way trying to convince people of a falsehood out of your sense of...something, I don't even know what.
In the English language, two negatives--"negative mishandling," to use Fowler's typically hilarious and sometimes dodgy usage--do not, in any way, resolve to or imply a positive.
I am a writer by trade, and even an educator during those college terms I'm feeling poor enough to teach English at the local university as an adjunct. I'm quite well-regarded in both fields, if I do say so myself. But let's set aside any suggestion of an argument from expertise and turn our attention to the four style guides used by professionals in the United States, the latest editions of all of which I conveniently, and unsurprisingly, have here at hand.
The Chicago Manual of Style, 17th Edition. This is the most widely used guide in American publishing, and is usually just referred to as "Chicago." It's the standard used by editors of fiction and non-fiction, especially copy editors.
The American Press Stylebook, 55th Edition. This is what journalists use and is commonly referred to simply as "AP."
The Publication Manual of the American Psychological Association, 7th Edition. Used mainly in academic settings outside university English departments (many History departments use it as well), particularly in the sciences, psychology being the most obvious. Usually referred to as "the APA."
The Modern Language Association Handbook, 9th Edition. As someone who has spent so much time in English classes, both as an instructor and as a student, it should come as no surprise that this is my favorite. We call it "MLA 9."
Collectively, to an educated, working writer and editor in the United States of America, these four books are "the rules."
None of those books make the, frankly, preposterous claim that double negation implies a positive.
I think your claim (in addition to being unsupported by any widely used and well-respected authority), is simply bizarre. Do you honestly believe that if someone says, "I ain't got no apples," that what that means, that the intelligibility of that utterance, is that that person has apples. Or, more to the point, do you honestly believe that they are trying to tell you that they have apples? Do you believe so to the extent that you would reply, "Ah! I see you are claiming to have some apples!"
Because that's what you're strongly implying.
I don't know how to convince you of this. You've chosen to die on this hill. And you don't look good doing it.
Sincerely,
Christopher Rowe, BA, MFA, writer of five novels, two short story collections, dozens of short stories, columns, and essays (and even one poem!), all of which were published by highly reputable and well regarded professional companies and many of which have been reprinted and translated around the world and someone who, to the minds of many at least, ain't no idiot.
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