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I've made a comment in the thread about the spoiler markup about this, but I think it deserves a feature-request now - we've been getting a lot of use of the spoiler syntax on gaming.
The spoiler box is great but it could really use some sort of message telling viewers it's a spoiler, otherwise it looks like a badly-formatted answer on first glance - especially for users unfamiliar with SE sites, the kind of users we also cater for and try to draw.
I think having some sort of "SPOILER - hover over this to reveal text" message is important. If this is technically too difficult, maybe just add it as a small-font red message just above the block.