I didn't find this to work. One minor problem must be corrected the '{' opening literal "Hello World" must be changed to '('. With both jumpers removed and a logic analyzer on the USART Pins I only get a brief high-low-high transition on P1.2 and nothing on P1.1.
Not obvious from most of the documentation, don't forget that the use of the serial monitor puts limitations on the max baud rate of 9600 even though the serial monitor offers options of higher baud rates.