If you really want to bet on BTC going down, you might consider a put option, rather than short selling. You can bet that a financial instrument will go down without borrowing money to do so and risking a potentially indefinite loss. You can always let a put option expire, and just lose the fee you paid for it. And right now, you shouldn't have any trouble getting people to accept such a put option, because most people want to bet on BTC going up.