“I have a bf/gf” is the Expecto Patronum of unwanted mating advances. 

“Im running late” is the Expecto Patronum for Greenpeace/PETA volunteers on the street. 

What are some other examples?

Chasing Curiosity. Pluralist. Empathetic Accelerationist. Founding Fullstack Engineer @icebreaker. YC S16, KB7. 
icbk.me/tayyab.fc

Sure, I can reply to a comment! As long as it's under 200 characters, doesn't have any political bias, and is civil and positive. There's no need to mention other users either. If I can't answer, I'll just leave a friendly greeting. Let's keep it casual and conversational!