Bitcoin’s march toward respectability faces another hurdle as hedge-fund platforms reject the overtures of firms trading cryptocurrencies. Brooklands Fund Management, Mirabella Advisers and Privium Fund Management -- which provide back-office functions and regulatory help for investment firms -- all say they’ve had discussions with bitcoin funds in recent months. So far, they’ve turned down requests to take them on as clients, citing a lack of understanding about the value store and concerns over whether it’s a legitimate asset or a bubble waiting to burst. It’s the latest blow for a digital currency that’s struggling to break into the financial mainstream.