Reddit mentions of OK: The Improbable Story of America's Greatest Word

It was the first word spoken on the Moon.

e: I'd like to also recommend the book OK: The Improbable Story of America's Greatest Word.

You might find this book interesting:
http://www.amazon.com/OK-Improbable-Story-Americas-Greatest/dp/0199892539

Edit: Removed affiliate code. Not intended as spam; my bad.

I'm assuming you're being tongue-in-cheek, but this is a world that interests me deeply so I thought I'd offer a proper response.

There are four points to your argument: 1) OK is an initialism, 2) initialisms aren't allowed, and 3) the proper spelling of OK is all capitalized, and 4) capitalized words shouldn't be allowed. I'll address each one in turn.

1. The etymology of OK is not settled. Some candidates include the Finnish word for "correct" (oikea) and a Scottish variant of "ah, yes" (och aye). If the current thinking around the word is of interest to you, I recommend Allan Metcalf's 2012 book OK: The Improbable Story of America's Greatest Word.
   
   
2. Initialisms are not categorically banned in the Scrabble dictionary. True, if a word is strictly an initialism, it is not permitted by Scrabble rules. However, "strictly" is a bit harder to pin down than one might think. AWOL was once a military jargon initialism, for example. It has since become a standard English word that doesn't need capitalization. The same is true for RADAR and SONAR, to name a few. Additionally, some initialisms happen to be standard English words; consider SAT or ACT.
   
   
3. The spelling of OK is up for contention, too. Merriam-Webster lists three valid spellings: OK, okay, and ok. Collins offers OK, O.K., and okay. The Scrabble dictionary is best thought of as a lowest common denominator. If even one reputable dictionary includes the word, so should Scrabble.
   
   
4. And finally, should capitalized words be allowed? Again, the Scrabble rules forbid proper nouns, but language does not care about strict logic. Countless proper nouns have become common nouns: TIMOTHY, MADONNA, HENRY, JAPAN, EINSTEIN, ALEXANDER, BRAZIL, FRENCH, ALASKA, OXFORD,...
   
   Language is neither cut-and-dry, nor is it stagnant. The spelling, denotation, connotation, and pronunciation of words are never fixed and are always subject to any one person's understanding and interpretation.