Why do my typed symbols disappear when I make a post?

[NintendoPie]

wfz said:

One of the most common faces to do on websites are these two faces:

1) =

2) =/

 

But whenever I type them, the forward/backward slashes disappear. What's worse, sometimes the entirety of my text that follows that symbol disappears as well when I post. Why does this happen on this website? It's been bothering me for years and it's never been fixed. I've also never seen anyone else complain about it. x_x

Are you talking about this face?

>_> >.>

EDIT: Wait... now I can't remember what face it is...

EDIT: Nevermind...