As promised, the WireHead forums now support spoiler tags! They work exactly like the standard bold, underline, and italic tags. Simply put your spoilers inside the tags and they'll be blacked out until someone highlights them.

Here's the proper syntax
[ spoiler ]omg INSERT CHARACTER did SOMETHING COOL and then DIED[ /spoiler ]

If you remove the spaces, you get

Yup, and it should work in private messages too, but I haven't tested it yet..

However, it will NOT work when exported as news for some reason, but that's not so bad as I can't think of any reason you'd want to put a movie/book spoiler on the main page...

Spoiler Tags are verified to work in PMs, for what it's worth.