The period was always the humblest of punctuation marks. Recently, however, it’s started getting angry. I’ve noticed it in my text messages and online chats, where people use the period not simply to conclude a sentence, but to announce “I am not happy about the sentence I just concluded.”

Say you find yourself limping to the finish of a wearing workday. You text your girlfriend: “I know we made a reservation for your bday tonight but wouldn’t it be more romantic if we ate in instead?” If she replies,

we could do that

Then you can ring up Papa John’s and order something special. But if she replies,

we could do that.

Then you should probably drink a cup of coffee: You’re either going out or you’re eating Papa John’s alone.

This is an unlikely heel turn in linguistics. In most written language, the period is a neutral way to mark a pause or complete a thought; but digital communications are turning it into something more aggressive. “Not long ago, my 17-year-old son noted that many of my texts to him seemed excessively assertive or even harsh, because I routinely used a period at the end,” Mark Liberman, a professor of linguistics at the University of Pennsylvania, told me by email. How and why did the period get so pissed off?