Right now, we don't remove comments that spoil or attempt to answer the question. This has always struck me as a weird policy, though, given how much people strive not to be spoiled in other places on the site.
I'm re-raising the question now, because recently, there's been an uptick in the number of flags we're getting on comments for spoiling some guess or revealing a solution to the question.
I'm also seeing that when someone does this, someone else invariably posts a well-upvoted comment asking them not to. This makes me wonder if the previous question is dated, and should be revisited.
Should we be deleting comments on questions that attempt to answer the question?
And, how far down does it go - what about attempts to make progress answering a question, without fully revealing the answer?