Even the snip tags show content on previews, don't think there's anything that can be done with it. I'm not an admin though, so I can't say for sure!
Only the first paragraph is previewed, so this could always be solved by waiting to spoil until the second paragraph. Also, I don't mind editing any opening posts that display spoilers in the preview so just slip me a note if anyone stumbles across this. I'm sure the other staff won't mind either, well, most of them anyway
