Yes, C across AIX, Suns, Silicon Graphics, whatever those HP ones were, and others. Platform differences were common, bugs rare because many had been before me and they could always be worked around; I didn't have to fix a C compiler. When writing a compiler the aim is to fix the compiler.
This isn't getting us anywhere. We disagree. I value the opinion of that lot given their many decades of experience. I used to have your opinion, based on textbooks. They've made a good point, one I can see has considered thought behind it.
Have you ever done multiplaform C development across using OS vendor specific C compilers?
There are lots of nice bugs to be found, just check the available bug databases of any C compiler.
So this does not make it any better.