XD is an overused emoticon and has 3 main states of use (xD, xd, XD)
how to use it
person 1: *tells joke*
person 2: hahaha that was so funny xD
how to NOT use it
person 1: Hi
person 2: XD
person 1: how was your day?
person 2: XD
person 1: .....
person 2: XD
person 1: please stop you XD bot
person 2: XD
person 2: XD
person 2: XD
person 2: XD
person 1: thats it *pulls wifi*