Whenever you see someone expose some bogus rule of usage, you can expect to see, almost immediately, a huffy comment from someone about the need to Keep Up The Standards. You will want to ask, "What standards?"
I draw your attention to an article by the Rev. Dr. David L. Chancey, "Everything I learned about grammar I blame on Ms. Brooks," published in The Citizen of Fayetteville, Georgia.
Ms. Brooks, who taught Dr. Chancey in the sixth and seventh grades, was evidently a piece of work, a grammar martinet of the boot camp drill sergeant style, and her strictures have been preserved in his mind as durably as the arthropods of the Burgess Shale.
Most of what he holds up is conventional and innocuous: Watch out for homonyms (lead/led, your/you're): remember that I is supposed to be a subject and me an object. Violations of the Standards cause him discomfort: "I can't just read for pleasure. A split infinitive jumps off of the page. A comma splice or a dangling participle begs for correction. Ending a sentence with a preposition — that's one of the worse grammar offenses I can think of ..."
I would like to hear Dr. Chancey speak, to find out whether he would case "What is that tool for?" as "For what is that tool?"
He also has an odd aversion to sentence fragments in spoken English, and their occurrence in the sports pages drives him up the wall. Ms. Brooks, presumably having paid her coin to Charon, is unavailable to question. I wonder whether she actually insisted that the conventions of formal written English must be applied to casual speech, or whether Dr. Chancey has taken a schoolroom oversimplification and universalized it.
In any event, the revealed truths of English usage which Dr. Chancey received from Ms. Brooks when he was thirteen years old have remained with him, obviating any need to learn anything further.
Not to hammer this Baptist divine further, I'll merely suggest that when you hear people talking about Keeping Up The Standards, these are usually the sorts of standards they are talking about.
The other thing to watch out for is whether the Standard Bearer is merely seeking to gain some social advantage over you. David Foster Wallace, in "Authority and American Usage" refers to himself and his family as SNOOTS, a private acronym meaning, variously, "Sprachgefühl Necessitates Our Ongoing Tendance" or "Syntax Nudniks of Our Time." Much as this playful self-mockery attempts to soften the snobbery of self-proclaimed language purists, we know what snooty means, and we do not privilege language snobbery above the other forms of snobbery.*
As a working editor, I know how difficult it can be to calibrate vocabulary and syntax to subject, author, occasion, publication, and audience. What is appropriate for the editorial page will look stuffy on the sports page; the tone of a feature on fashion will be out of place in an account of a shooting. Just as there is no one English but a variety of dialects, there is not even one standard written American English, but a spectrum.
Today, National Grammar Day, we would do well to remember Phillip Blanchard quoting Jonathan Kaufman: "EVERYTHING in English is 'generally,' plus 'sometimes.' "
*Were I a SNOOT, I would have written [sic] after worse in that last sentence from Dr. Chancey I quoted.