Tagging system to prevent spoilers

ideaorama:

A system for marking up text to allow for variable disclosure of
information or alternate information based on user controls - (ie the
content of a companion site would display information only up to specific
points in the plot that was desired) - Dumbledore [sp (t>b6c27)?is|was]
headmaster of hogwarts]

Check out http://towerofthehand.com/  and click on the Scope div.

This made me really happy, and then really sad that it’s not actually a thing.