Excerpt from this article:
I went out with a guy based on his use of dashes once. Within moments of our first interaction — over text message — I was basically in love.
He didn’t just use the lazy singular dash (“-”) as a pause between his thoughts, or even the more time-consuming double-dash (“–”). Nope. This man used a proper em dash.
That is, the kind that required him to hold down the dash button on his iPhone for that extra second, until the “—” appeared, then choose it from among three options. I don’t remember what his messages actually said. But he obviously really liked me.
…It’s also as if a kind of micro-punctuation has emerged: tiny marks in the smallest of spaces that suddenly tell us more about the person on the other end than the words themselves (or, at least, we think they do).
…“Digital punctuation can carry more weight than traditional writing because it ends up conveying tone, rhythm and attitude rather than grammatical structure,” said Ben Zimmer, a linguist and the executive editor of Vocabulary.com. “It can make even a lowly period become freighted with special significance.”
And so we’ve begun to think our friends are angry when they respond with a period, or weird when they capitalize the starts of their sentences. We insert extra letters (“loooool,” “sooooo,” “hiiiiiiii”) — what linguists call “affective lengthening” — to convey intensity, and remove them when we want to be aloof.