I remember when HitBTC was one of the most popular STEEM and SBD exchanges. Then HitBTC shut down their wallet preventing any STEEM or SBD from going in or out of HitBTC back in February 2018.
All that STEEM and SBD got stuck in the HitBTC exchange wallet. While individual users of HitBTC could still trade STEEM and SBD, none of that cryptocurrency could leave the exchange.
About 6 months later HitBTC sold a bunch of that STEEM when the price was still high. HitBTC effectively stole that STEEM currency. It is all on the STEEM blockchain
Anyone can go and look for themselves https://steemitwallet.com/@hitbtc-exchange/transfers
What is even worse is that they continue trading STEEM and SBD against Bitcoin even though their wallet has been abandoned. They are not trading STEEM or SBD. They are trading a virtual version that has no tie to a real functioning wallet. So essentially, they are trading fake currency against Bitcoin. That essentially makes Bitcoin on their exchange Fake as well.
Why did they do this? My guess is that they have insolvency issues (they owe more than they have). Perhaps they created virtual currency that doesn't exist to cover their bills. For instance, they could have created a virtual supply of Bitcoin or some other currency and sold it to their customers on their exchange.
The moment that a government entity steps in and audits their exchange, they are going to be in big trouble. I don't know how they are going to explain how they were trading a fake currency for over a year now.