Here is a thought that came out of this discussion: http://storiesonline.net/d/s2/t1226/noticed-an-amendment-to-the-submission-coding-advice
Some authors have stated that they may not want to include certain codes for a particular story even if it's a major element and a possible squick because it could give away a plot twist.
The caution tag was mentioned and rejected as well as a "Surprise" tag was recjected as well, both for tipping that there is a surprise.
Then CW mentioned a "Hidden Tags" tag.
That gave me the following idea:
Allow authors to fully code a story but designate certain codes as "hidden"
The hidden codes would not be displayed to users on the story lists, but they would be used for category searches and category exclusion preferences.