What we do know is that their own website T&C says by holding a USDT token, they owe you nothing. They never have to allow anyone to withdraw a single penny. They can sail off to a (different) island and keep any assets they may or may not have, scot free. They're chuck-e-cheese tokens.
They hired an auditor, then the auditor quit.
They bank with a domestic bank in the Bahamas, Deltec (chaired by the creator of Inspector Gadget, Jean Chalopin), who they may well own. Just as they owned Noble in Puerto Rico before it was bankrupted due to their ownership being revealed. And guess what? The Bahamas' government domestic bank foreign liabilities do not show a 24B influx of USD over the last year.
There's no reason - nor has there ever been reason - to believe Tether is anything other than a scam to enrich Tether and bank Bitfinex. The crazy thing is that USDT volume amounts for 80% of BTC trading volume. [1]
I just can't understand the "well, let's just assume it's fine until proven otherwise" attitude. If that's your attitude I've got a tokenized bridge to sell ya.
To call Tether a systemic risk to the entire crypto space is quite the understatement.