Let me make myself clear, as I didn't do so the first time. This is what I think (regardless of the law or convention).
If someone writes, emails or talks to me about themselves then it is confidential unless I have their permission to pass on what they have said. On the other hand, if someone writes, emails or talks to me about me then what they say is mine to do with as I please. If you have something to say about somebody else that you don't want anybody else to know you've said then you should just not say it in the first place.