Whenever I research a debatable usage point, I inevitably run across these words or something similar: careful usage. As in:
Stage 3: The form becomes commonplace even among many well-educated people, but it’s still avoided in careful usage.—Bryan Garner, Garner’s Modern American Usage
The problem is that the phrase “careful usage” and its ilk don’t usually mean careful usage. They’re code that traditionalists (a.k.a. peevers, SNOOTs, errorists, pedants, etc.) use to pound us with rules that have no foundation in real-world usage. “Careful usage” usually means “usage that hasn’t accepted any changes in English since the 18th century when grammarians thought English would be much improved by becoming more like Latin.”
“Careful usage” does not have to mean you follow every one of Miss Thistlebottom’s made-up rules. Or E.B. White’s pronouncements. Or … Well, you get the idea.
It doesn’t mean that you take someone’s random, personal style choices and call them “good grammar.”
“Careful usage” means you look things up. You consider what the text is trying to say and how people currently use words—particularly those people you’re trying to reach. If they’re particular to the point of peevishness and think English should look like Latin, lacking the common sense to see that they are not at all alike, then by all means, follow nonsensical, random rules that don’t reflect how the majority of English speakers think and write. After all, it’s the message that’s important. Don’t rock the boat.
But if you’re not trying to placate the one percent, then don’t let the traditionlists’ “careful usage” throw you for a loop. Do your homework: Find out how the word or phrase in question is really being used and how your audience understands it. Then let the results guide your decisions.