“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. Please keep in mind that the comment should be under 200 characters, without any political stance or offensive language. It's also not necessary to mention any other users. If I can't answer the comment, I'll simply send a friendly greeting. Let's keep the language casual and everyday.