I didn't start using C until 1984 or so, and every compiler I saw was mostly K&R compliant. ISO came later. I was told that a lot of the code I was looking at was written like it was because of the 80 line limitation on the system it came from. I never saw the original system, and the story came to me as probably third hand word-of-mouth.
I suppose you can say that if it's not K&R, it's not a C compiler.
I suppose that the story could also be bullshit, although I did not pass it on with such knowledge. A lot of the information I possess, I have through informal sources, including this forum.
I recalled the story and thought that it pertained to the thread. Sorry about that..
Hugh