Should the ## Rationale section be more detailed or explicit here? I’m generally in support of verbose rationales and non-normative implementer guidelines, tag me if you open a PR on those.
Is this a question for the spec or for reference implementations linked to from the spec? I can imagine reference implementations modeling good behavior by describing the shape and semantics of its Context property in their readme files for quick reference? Not sure if the spec should tell anyone they SHOULD do that, though?
One man’s breakage is another man’s upgrade path 
All joking aside, I think the co-authors of this proposal have discussed the breakage and are OK with it. Would more ## Rationale help here as well?