At a time when nerves are stretched to the point of snapping and every political issue seems to verge on the apocalyptic — climate change; immigration; gun violence; race relations; what the president said or claimed to say or did not say about China — it might seem needlessly picayune to dwell on the writing style of the occupant of the White House.

But for people who care about the English language and how best to use it, President Trump’s continual flouting of even basic writing conventions is a serious matter indeed. Mr. Trump’s impulsive tweeting and concomitant error rate seem to have grown this year as his frustrations with topics that upset him, from the Mueller report and the House speaker Nancy Pelosi to immigration and 2020, have intensified. On Friday, in a bad-tempered Twitter screed about one of his current preoccupations, the Federal Reserve, he wrote that he was “reigning in” bad trading partners. On Saturday morning, he congratulated Sean Hannity on “being the number one shoe on Cable Television!,” though the message was later corrected.

After he has spent nearly three years in office, Mr. Trump’s critics ask, why does he remain intent not only on making egregious errors, but also on deliberately failing to correct them? Leaving aside its splenetic tone and in-your-face ad hominem attacks, knee-jerk defensiveness and ugly, dog-whistle language, why is so much of the direct communication from the president to the world heaving with bad grammar, bad spelling, bizarre punctuation, muddy diction and inexplicable random capitalization?

“If you care about literacy and the correct and accurate use of language, then this president has got to be driving you crazy, regardless of your political point of view,” Mr. Garner, who says he is apolitical but considers himself a liberal Republican, said in an interview.

The Democrats hope that in 2020 the country will elect a new tweeter in chief, perhaps even one who knows how to spell. But Mr. Trump’s Twitter style has served him well with supporters who applaud his maverick resistance to rules. So far, no other politician has managed to pull off his sui generis mix of pugnacious content and my-way-or-the-highway approach to English composition.