For example, there's a note that says
> Specification authors should avoid using callback interfaces that have
> only a single operation, unless required to describe the requirements
> of existing APIs. Instead, a callback should be used.
It's not clear to me if this is normative, and if this recommendation is on the same level as the pink warnings, which seem to be similar in subject (legacycaller, integer constants...)
I upgraded that and another Note to a Warning, so that they are normative.