What if it's a photoshoped document all together, don't think banks are legally allowed to confirm it to outside parties? Anything outside of full audit by big four is pretty useless, so why bother
Banks share information about their customers all the time. That’s how credit reporting agencies get their data.
I’m inclined to believe that the letter is real and that Bitfinex really did have $1.8 billion in cash on that particular day. If the letter was fake, the bank would have said something.
Binance supposedly earned over a billion dollars last year so no reason why Bitfinex / Tether couldn’t earn $2 billion over 5 years.
That being said, I think it is unlikely that Bitfinex just leaves the money lying in the bank account. They want to earn interest on it. Some is probably invested in US Treasuries. Where it gets dangerous is if they are getting cute around the margins and buying large quantities of junk bonds in what appears to be the tail end of a bull market. Their cash management strategy could blow up. The Big 4 won’t touch them with a barge pole because the management are all cowboys. Far too risky.