And if you use it with p tags, it can be really annoying (Preview mysteriously disappears/freezes, preformatted text doesn't work, even elsewhere in the post).
But, I found a way to cheat the system. Just put </span> after each @ sign.
They mean, "What does @ have to do with anything?"
@spacer: @helicoptur is saying that what makes scratchblocks not work in the first place is using @ in the scratchblocks text (I'm guessing because that conflicts with the forum using it to cite usernames).