I think my favorite use of emoji responses on Slack/Discord/etc is when someone just latches onto a particular word in a message and attaches its emoji, with no semantic content intended. E.g. someone'll say "Sorry, the bus is running late" and someone else will just slap a 🚌 on there to confirm that they did indeed notice and recognize the word "bus"
@danbruno 🏃🏻
@danbruno 🅱️🇺🇸
@danbruno the digital version of driving past a field with horses and saying “horses” out loud