Oxfordcomma
Challenge Tour Pro
My understanding is that it's the GM Forum that would have breached the DPA - as the organisation that provides the environment on which the private data was published!
You are correct however - in that the DPA applies to 'organisations, businesses and the government' and not to individuals. That's why it would be the Forum's responsibility to remove the personal data - certainly if requested.
If they declined to remove it, then you could use reference to the DPA to require it to be removed by Forum management! But yes, it's unlikely that you would need to actually do that anyway - it was a (supposedly) deliberately trivial example.
Foxholer, as you say it's all a moot point but I'm not sure I agree with your understanding. GM is liable if this forum is used to defame someone, that's where it becomes relevant that they are the organisation that provides the environment. Data protection isn't applicable though if someone's details are posted by a 3rd party individual, because GM has not obtained those details for themselves.