I have seen it coming more frequently these days, that people are so excited that they write spoilers. It is usually happening at the Manga/Anime section and that doesn't surprise me at all. xP

So, I'm not sure if anyone found out the code for the spoilers yet, but they exists. I didn't even know until now, since I never really bothered to look up. I know that I'm a bit late, but I hereby present you guys and girls, the code for the Spoiler "Tag". x]

First, click on "Others" that is located at the reply form. It's at bottom left. Click on Spoiler if you want to hide something that could spoil something.
It'll look like this:

Spoiler:

Testing 1 2 3

If you want to read the spoiler, you'll have to click on the bar, it's easy as that. ^^
So, give it a try, you anime/manga fans out there. =p

Sincerely,
Ami