Seeing another person’s facial expression no matter how brief elicits a response of our own. The human mind can then process this information at 13 milliseconds and is able to understand and respond accordingly.
I’ll bet you have most probably had a similar text conversation before: “I’m bringing takeaways, I’ll be home at 6.” “K” “why just k? Is something wrong? Should I rather be cooking for you?” It seems to be a piece of advice so often given but so rarely taken - do not communicate important issues