The latest edition of Collins Official Scrabble Words includes 2,862 new entries, among which is OK. But that’s “a controversial choice among players, as according to the official rules, it should not be allowed due to being both capitalised and an abbreviation.”
But honestly, it’s the least controversial thing about this article.
2016 World Scrabble Champion – yes, that’s a thing – Brett Smitheram is quoted as saying that the inclusion of OK would be “one of the most impactful changes” to the game. That’s right, folks: The man who was once the best Scrabble player on the planet, in a defense of the new and improved official list, used “impactful” in a sentence. Unironically.
Pretty sure that alone disqualifies anyone from pronouncing an opinion on what is, and isn’t, a word.