I've seen a few edits in the suggested edit queue that consist pretty much entirely of people inserting spoiler markup for questions. I understand why it's desirable, but I'm wondering if the decision to mark something as a spoiler shouldn't just be left to the answerer themself.
At the moment, we don't have a solid consensus on whether answers should be in spoilers. There is some discussion on the topic here, but it is clearly not definitive and shouldn't be taken as policy. Until and unless the site reaches a consensus that answers giving the solution to a chestnut / gem / puzzle should be in a spoiler, edits only or primarily to add such spoilers should be rejected as "too minor."