That seems like a lot of work for something that still won't solve your problem.  To summarize:

- Spoilerific sites *already* have (and follow) rules about no spoilers in *titles*, which is all you see on the HNQ.

- Spoilerific sites *already* have (and follow) rules about using spoiler markup in post bodies.

- You're asking for manual use of a meta tag (against SE norms, additional work) to block the question from HNQ entirely (overkill) lest you bypass the spoiler warning and look anyway (avoidable).  If we need to do anything, there's a better way than what you propose.


Right now you're asking *everybody* to forgo questions that would otherwise be shared because of a concern about spoilers in *some* of them that can be avoided by not clicking (or hovering, if you do click).  Shouldn't these sites, and the authors of their hot questions, have the same opportunity for network-wide exposure that others have?

Further, it wouldn't solve your problem.  Meta-tags like this are discouraged across the network, so getting users to do it here for reasons **external to their site** is going to be an uphill battle.  Instead, these sites rightly focus on things that matter to *them*.  **Manual, extrinsic meta-methods don't work.**

If we decide that entirely blocking questions with spoilers is desirable, we don't need to push sites to do meta-tagging.  The system could automatically filter from the HNQ any question that contains a spoiler block.  That at least would be an automatic method; it relies on people using those spoiler blocks, but sites that care about spoilers are already enforcing that.  I believe the HNQ already filters out questions containing certain words in their titles, so maybe adding this check is feasible.

Barring that, I recommend that you not click those questions, or that you use a userscript to filter your own HNQ list.  Three days after *The Last Jedi* came out, what are the odds that an HNQ about it *didn't* contain spoilers, after all?


Related:

- https://meta.stackexchange.com/questions/214137/weight-hot-network-questions-sidebar-by-viewer?rq=1

- https://meta.stackexchange.com/questions/90885/can-you-filter-out-certain-se-sites-from-the-hot-questions-list

- https://meta.stackexchange.com/questions/222721/how-to-avoid-hot-network-questions-on-the-sidebar