I was just curious that's all. I would guess a large percentage of the float is held at IB so it would only make sense that their are shares to short unless they are being restricted in some way by IB in which case I'm curious why they are restricting it.
If they are confident in their business then why the restriction, if there is one? They should welcome the shorts.
IBKR is a volatility play. Something like 80%-90% of their profits come from market making and proprietary trading. If volatility increases then so should their profits.
The brokerage side of their business is nothing and means nothing really to their bottom line. Everyone who has an account their, including me, loves their product and think it's a great platform and it is, but that's not the story here. The story is the market making and proprietary trading, nothing more.
Read the S&P report on their site if you want to understand their business.