Are Mercy and Moira connected?
Good and evil. Light and shadow.
We don't know much about new Overwatch healer Moira, but it's hinted at that she's had some sort of relationship with Mercy. It seems they were once coworkers at Overwatch, though Moira was later shunned for her experimental morals. Mercy is good, and Moira is evil. And during BlizzCon, Blizzard hinted at Moira's tech, noting that it has suspicious likeness to Mercy's.
Mercy and Moira definitely have a history—but until more comes out, we only get to speculate. The thing is, there's a lot to speculate on. Once Moira was released to Overwatch's PTR, all of her unlockable cosmetic items became available, too. A few of her sprays suggest a relationship with Mercy.
Reddit user chomz147 noticed similarities between two sprays, both of which show Mercy and Moira in their Overwatch and Blackwatch outfits. Put them together and they appear to create the organizations' logos.
Two other sprays, Shadow and Light, are extremely similar.
Moira will likely be on Overwatch's PTR for quite some time before she's released into the official game. Blizzard has not yet detailed a timeline. As with other hero releases, it's likely we'll learn more about the new Overwatch hero in the lead-up to her release on PlayStation 4, Xbox One, and PC.
All we know right now is that Mercy and Moira are connected in some way, but it's up to Blizzard to unravel the story for us.