Note that the specific failure case that Davis is mentioning (there’s a hole in Person C’s context) is unrelated to the failure case that you’re mentioning (person C might reply to person B, which person B doesn’t want).
It might also be that “person B doesn’t want person C to know anything at all about person B, including that person B is responding to this conversation.” Perhaps that’s an unreasonable thing to prioritize over person C’s context, but then you’re just conflicting different people’s values.
Note that the specific failure case that Davis is mentioning (there’s a hole in Person C’s context) is unrelated to the failure case that you’re mentioning (person C might reply to person B, which person B doesn’t want).
It might also be that “person B doesn’t want person C to know anything at all about person B, including that person B is responding to this conversation.” Perhaps that’s an unreasonable thing to prioritize over person C’s context, but then you’re just conflicting different people’s values.