I don't think that this site requires spoilers. As others have said, the myths are largely centuries old, and therefore, spoiling is pretty unavoidable.
(The comments you pointed to were indeed tongue-in-cheek - I started writed the question, and instinctively thought of spoiler-marking "beheading" as I would for a newer story.)
The one exception might be potential questions about modern adaptations of a myth that change an element of the myth (and this is completely hypothetical, I've no idea if it would ever happen). If, for example, there is a TV or book series doing a modern adaptation of a set of myths, and kills off a character unexpectedly, and someone wants to ask a question about how this relates to the original myth, I would courtesy-spoiler the new death. However, that's pretty much the only situation I can imagine anything spoilerific being mentioned here.