Expanded example: I just read a great story where the rape was just DROPPED IN to the middle of a paragraph and I would definitely have appreciated some kind of heads up. So, if it were my turn to pick for book club and I chose that story, I would include in my blog entry, somewhere visible, "Content note: rape" or some such thing (like the parenthetical above).
Or, if I were recommending this historical essay I've been considering about early American schools, I might include a (Content note: Descriptions of violence, corporal punishment), as a fair warning for anyone who wanted to put off reading about those things until they were feeling better, or just appreciated being mentally prepared to read about a lot of sixteen-year-olds getting beat up in various contexts.
The problem is figuring out when to include content notes & how specific to be -- but that can be a subject for discussion. It's fairly easy to do this on a common-sense, your-own-best-judgement basis and fine-tune it as we go.
What do you think?