Don't worry about this at all. In my opinion, we have not done anything that can expose us to liability. My assessment is based on the following facts. Please correct me if I am wrong.
(a) We don't have any personal information about John; and
(b) We haven't given any information about John out to anyone.
So long as both of these assumptions are correct, John cannot bring any claim against us.
Federal law grants operators of interent web sites sweeping immunity from liability for activities associated with the operation of the sites. Operators of web sites generally do have a duty to keep the personal information of the site's users confidential. It is also unlawful for the operators to knowingly permit unlawfal material to remain posted on their site, such as material that infringes someone's copyright or trademark rights.
However, most other activities relating to the operation of a web site have immunity from liability under federal law.
The foergoing discussion is based on US law. John lives in the UK, so it is possible that he does have a claim against us under English law. I don't know anything about English law- but I am not worried.
In order for us to become subject to liability in any legal system, we'd have to do something. We'd have to harm John in some way. But the he beauty of the present situation lies in that we haven't done anything! We can't possibly harm John, because we don't have any information that could harm him. We don't even know who he is! His concerns about our "release" of "personal" information are groundless. We have no such information; nor have we released any.
I don't know what to make of John. I have long suspected that he is scamming us, but I have never said anything becuase I had no proof. His first email to David almost convinced me that he has been truthful. But the recent flood of messages has me scratching my head again. Is he self-destructing like criminal defendants sometimes do? Or is he a concerned husband? I just don't know.
In sum, though, do not worry about being sued by John. If you'd like, we can assure john that (a) the individual (Boyer?) to whom he referred in his email to Redcarguy has been banned, and (b) we have no personal information about him- nor have we ever had it- and have never released any information about him or his wife to anyone.
If John continues to cause trouble, we can always ban him. Let me know before you do this, though. There's a right way to do it.