There must be some rule or something about impersonating site staff right? Is there some way to take action against whoever the person spoofing their address and making these bogus claims?
Just a quick follow-up, but after even more in-depth investigation, it appears that it probably wasn't intentional.
It turns out that when you send someone an email through the forum by clicking on the mail icon by someone's name, it sends it with the source's email address as the display name and the Reply-to address, but uses the default site "webmaster" address as the from email address. In this case, it was stamping "admins@cohtitan.com" on every message sent through it.
Needless to say that's not a good thing as it can lead to exactly the kind of confusion seen in this thread.
It appears to be a deficiency in the forum software as there's no way to configure that, so we've patched our local copy to use the correct "From" address and I'm going to submit a bug report to the makers of the forum software and see about getting it fixed officially. That's not correct behavior IMO.
So I'm somewhat less annoyed now. At least more of it is directed at SMF than any particular person here.