Ripple is actually not a blockchain, but a distributed ledger technology that relies on a different kind of consensus protocol (it doesn't really matter what it is for this discussion), Ripple is very reliable and robust for the user above commenting about bugs, it's way beyond that at this point and is being used to process hundreds of transactions per second. However, more pertinently it could make sense to integrate the Ripple protocol in that Bunq could become a gateway thereby being able to issue fiat IOUs on the network for the process of sending and receiving international transfers. However this isn't as simple as only participating in the Ripple protocol and would require exogenous legal agreements to work as desired. Also this is a higher level implementation detail that Bunqers need not worry about as they wouldn't interact with technology if it was implemented, the concern of Bunqers in this regard should pertain to the speed, cost, reliability etc of transactions and not their implementation details.