This isn’t just for funsies. It’s company policy to use certain emojis to indicate certain communiques, such as a meeting summary. If he forgot the bear, team members could miss important decisions.

“My favorite team value is over-communicating,” says Mr. Nowak, who is now a self-professed emoji fan. “If you hesitate to write a message because you think three-quarters of the team already knows, that’s not a problem, you just preface it with the ‘over-communicating’ emoji.”

This is how formality in business communications dies, not with a whimper, but with a parti-colored riot of modern-day hieroglyphics, denoting everything from collaboration to dissent. At Slack itself, employees use the “eyes” emoji to indicate they’re reading a just-posted memo. The “unamused face” or even the “nauseated face” are both acceptable in communications channels at Joyride Coffee, a Woodside, N.Y.-based beverage maker.

This trend is much bigger than the latest thing the youths are foisting on their crusty elders. It’s happening for deep neurological reasons, according to recent research, and can lead to better cooperation. But that doesn’t mean it’s always appropriate to use them, or that they can fully replace other forms of communication.”