Below is the legal explanation I received from Tempest, who gave permission to share it with those who are seeking clarity on the issue (I added the bold-underline):
"One of the more touchy-feely bits you get admonished about when you scribble on your SF-86 and go through the process to get a clearance, is that there can be no participation in groups, communities, social circles, clubs, etc. that solicit classified information (even if it’s frowned upon in that community, or a one-time affair, or done by outlier members of that community). This policy is particularly “zero-tolerance” when it comes to individuals possessing a TS (which he does), and even moreso when it comes to highly important platforms and systems (which the F-22 happens to be).
As such, to rephrase his words on the matter, he didn’t really have a choice but to abandon ship when members of the PRC-leaning, PLA-focused forum which he had already been “playing classification chicken” with (to use his words) by writing extensively on the more technical aspects of military operations and weapons systems (to the extent that some of his works are the most complete, comprehensive, and competent analyses available on the internet vis a vis their subject matter) began repeatedly requesting that he disclose and disseminate classified mission systems, data processing/fusion, signature management and emissivity profile, and integrated networking technical specifications despite making it clear it would be unlawful to do so.
Well, that is, unless his goal was to, at best, lose his clearance and career by violating those aforementioned OPSEC constraints regarding even being around individuals or groups doing so; or at worst, his freedom, by committing Felony Espionage in violation of 18 U.S. Code § 793 (Gathering, Transmitting, or Losing Defense Information).
^ In light of this, I totally understand him leaving the forum. No amount of 'warnings/bannings' on an internet forum would fix this problem, so it's pointless. This is an actual legal issue and internet 'bans' are meaningless in court. As soon as the first person asked him to divulge classified data, he was legally obligated to "abandon ship" immediately, which is what he did. Not because he wanted to, but because he had to legally.
Sigh... I guess the moral of the story is that IC and OSINT don't mix. It's a loss for us, because he was a very valuable asset. In his short stay on this forum, many of us learned a lot from his posts and he clarified a lot of things that a bunch of us were going in circles about for a long time.
