Blizzard has applied for a patent for the Play of the Game replay system (and the systems that support sharing them on social media) by the US Patent and Trademark Office. The patent application was only published earlier this month after being filed in 2016.
The patent document outlines how the system works with the game timestamping notable events in a match. Interestingly, along with the High Score category, the patent also included Lifesaver, Sharpshooter and Shutdown categories.
Source: N4G PC Blizzard Applies for Patent on Overwatch's Play of the Game System