I know the particular thing I see shouldn't be a big surprise, but if I go to Stack Exchange's home page, I'd like to not be greeted with a major story point for a movie that just came out today. Other sites such as reddit have strict moderation to keep this stuff off of their front pages.
What counts as a "spoiler"? For how long (warning: link goes to a comic with vulgar language)? Recently on SciFi, there was a small controversy over the title of a question about a minor plot point in an eight-year-old book.
These titles are also only a concern for sites that are deal with popular culture, which is not very many of them (four or five, maybe). It doesn't seem worthwhile to develop a feature targeting so small a part of the network.
On the other hand, given the grief that the HNQ list seems to cause sometimes, perhaps a generic way for moderators to remove a question from the list that they otherwise like and want to keep would be a good idea. Then each site could decide how they wanted to use that tool: if one of them decided that keeping "spoilers" off the list was important, they could do that.
You probably refer to this question currently appearing at SE home page at top
Well, the movie is out in the wild now, and to prevent yourself getting spoilers until you've got occasion to watch it, just don't click anything containing "Star Wars" or "The Force" in the title.
What you're asking for is way off for a feature request on Stack Exchange, or applying any censorship from moderation.
The site is very different from Reddit, and that's incredibly good so.
If you want to prevent yourself reading/watching spoilers about Star Wars "The Force Awakens", there are already tools available you can use. Or just stay off the internet as it was mentioned in comments on your question.