Does switched-mode power supply feature galvanic separation?
Not all SMPSs provide galvanic separation. DC/DC converters transforming between two low voltages in a circuit often don't. The block diagram, however, shows a mains connected SMPS, and most of those do have galvanic separation.  

The feedback often goes via an opto-coupler, which indeed is missing in the article's block diagram. The signal is PWM, so a normal (digital output) opto-coupler can be used.