The currently go-to link for stance is this link, where all dupes redirect to: Of spoilers, plot twists and our mission. The sources from there all date back to 2013 with no update.
Currently I have a debate going on within one of my own questions. A user has engaged in a rollback war and insists that spoiler markdown is an unnecessary addition to a post. However, the highest voted answer on the source linked above indicates that having spoiler markdown on a question's body (and subsequently avoiding a spoiler in the title) prevents users from accidentally seeing it from the question excerpt in the Questions page.
What is our currently held stance on spoiler markdown? Does the old source hold true or are we attempting to do away with spoiler markdown?