Are you able to put character symbols in your Facebook name?

I’ve seen some people do it such as a girl on my Facebook her name is shown like this: Jesselyn ✯ <—-with the character symbol.
There’s another guy on my Facebook he had his Facebook name in Arabic. So I was like, “you can change it to the way you want it? Well Let me try it myself.” I went to put a character symbol on my Facebook name but it wouldn’t go, I tried putting it in the front, middle and in the back of my name but none of those would want to go. I also tried changing my Facebook name into Greek but it didn’t allow me to change it.

So I was wondering how is it that they’re able to do it and I can’t? Did they do it with a cheat code or something or is Facebook just being kind of picky of whom it would like to have their name changed the way they want?