This was previously submitted[0] and deemed "unconfirmed". Does it showing up on the TempleOS page make it any more official? Who runs the website in his absence to make this update?
There is additional proof, from his sister's Facebook page, but I'm not sure I want to link it here because it seems rude to link his family's pages to random people. Is there a moderator here whose email address I can message with the proof?
Though Wikipedia already has such a link confirming it. I don't think you need to prove it.
Edit: Or did. I can't find it now. I was sure there was a really short page for him on Wikipedia when I looked the other day. At the moment, he only appears on their disambiguation page without a page of his own. It also shows a death year of 2018.
It's a pity we never could be inclusive enough to take someone in who clearly needed a bit of support. Terry definitely was a troubled person, there is zero doubt about that but if you looked past the sillyness (which I understand is hard in an environment that puts great value on political correctness) he was a really nice guy with some surprising quirks and a good sense of humor. On off days he was not so nice. Nobody's perfect.
Maybe this will live on as a "Terry's death was never confirmed" (Andy Kaufman style). Would be a pretty cool way to memorialize him. Not sure if that would affect his family negatively though.