This configuration will not be harmful to the device and is often used in circuits for a sort of loop-back setup. The customer will need to understand that when /RE is low and DE is high, the receiver will be receiving everything that the driver is sending – this is called loopback – so they will need to address this in software. Sometimes customers use this configuration to verify the data being sent on the bus (as a sort of integrity check). If this is not what their purpose, then they will need to be sure to ignore any data on RO when DE is high.