I'll explain as best I can.

Guy posts on the forum: "I know a secret, and I think you know it too."
Guy doesn't want to reveal the secret in public, so tells me privately.
I didn't 'know' the secret, nor is it public knowledge.
Guy can't yet reveal to anyone what the secret is because the sources aren't public.
Outing his sources would likely damage those sources.
While I could reveal the secret, it would damage both Guy and his sources.
The actual secret is relatively unimportant for everyone and unless someone sues someone else, isn't even an ethical violation.
There isn't any reason for me to force the issue of revealing it.

The end result of what Guy said is that it makes it out as if there is some big conspiracy when its a very minor thing we don't actually care about. But now no one can confirm, deny or explain. It wasn't a good idea.