Ezra Marcus writes about Tone Indicators for the NY Times:
Today’s tone indicators go a step further than, say, putting a winky-face emoji at the end of a sentence. They assign a narrow, concrete meaning to a statement, leaving no room for interpretation. They are not subtle and can deflate humor. (Picture a comedian declaring to an audience “I am joking” after saying something outrageous.)
Writers add a /indicator to the end of a paragraph, like /rh to signify that something is a rhetorical question or /hyp to indicate hyperbole. It’s an interesting strategy instead of simply skipping anything nuanced. I am old enough to still consider the phone the solution to anything other than a brief email exchange, because email exchanges often go so very wrong, so very quickly.