The bottom-line fact is that there's no single, universal bottom-line standard. Use the SAAMI "rule" in whatever you write, if that's your personal standard -- but don't insist that it's a universal standard or that any other convention is wrong.
When Ed Matunas was one of my writers, and I his Editor, I suggested this compromise, which ever-amiable Ed readily agreed-to -- I wouldn't insist that he use the decimal in his manuscripts, and he wouldn't bitch that I was "wrong" to use it in the magazines. That's how we handled the matter.
And get over the notion that it's "language" or "grammar." It's neither. Either way is merely a printing convention, just as initial caps, periods, commas, etc, are unpronounced marks, not elements of language or grammar. (Language is what we speak -- sounds. Grammar is the way we arrange our words into meaningful strings called sentences. We don't say, for example, "Capital W when capital I go to town tonight comma capital I intend to buy a couple of sacks of potatoes period."
