How do you set a message like this?

lankaino · November 11, 2015, 9:24am

This person has “afk” above them.
How do you set a message like that, and it stays there.

MadHatter · November 11, 2015, 9:25am

Type “!!” without the quotation in the chatbox. For example “!!afk” and then press Enter. Voila.

lankaino · November 11, 2015, 9:34am

Thanks, that works.
Now how do I remove it? xD

-Edit-
Never mind, I figured it out.