Sometimes, especially in a mystery story, the results of a challenge could be a spoiler. This is even if the player is making up most of the details; sometimes the nature of the potential details is a spoiler.

Similarly, there might be times when the narrator wants some text to be only available to certain players, say, during a narration. (I'm imagining a situation where some characters notice some details, and some notice others.)

The solution would be a "spoiler" tag like many forums have. It would either make the text the same color as the background (highlight with your mouse to see) or use javascript to create a "Show/Hide" button for tagged text.

This would be all on the honor system, but a lot of the game is already on the honor system anyway. More importantly, it would have a lot of potential uses, once implemented.