I just added a new feature... the spoiler tag!
If you surround text with [spoiler] OMG, Vader is Luke's father! [/spoiler], it will appear in your post as this:
[spoiler] OMG, Vader is Luke's father! [/spoiler]
Cool, eh? It's something I've been meaning to add, but didn't get to it till now. I'm going to be fiddling with it for a bit to make it look all pretty, but if you're wondering what the new "Sp" button on the post screen is... well, there you have it!
Please note that you don't need to post things behind spoiler tags if you're in a thread with "SPOILER" in the title. But in other threads, here's a way to do it instead of making the text black or leaving space or whatever people have been doing up to this point.