The recent addition of Moira, the new Talon support, to the Overwatch character roster has brought to light some interesting lore for Reaper. The former Blackwatch commander has been depicted as nothing more than a shotgun-toting, skull-wearing villain in the past, but with Moira's release, we have been able to see a little more into his background.
It was often thought that, due to in-game voice lines, cinematics, and general fanbase agreements, Gabriel Reyes was furious he wasn't chosen to be Strike Commander of Overwatch. Instead, the title went to Jack Morrison (Soldier 76), a man he had fought alongside and become friends with during the Omnic Crisis. It was speculated that this choice by the United Nations caused a rift between the two, leading to high tensions that ultimately destroyed their relationship, along with the Overwatch Swiss HQ.
However, a recent Q&A session between twitter user @Autolikescake and Jeff Kaplan, reveals that not only was Reyes supportive of Morrison's promotion, he was relieved that he wouldn't have to be put in a political role himself. Whilst Jeff does admit that Blizzard hasn't "explained it well" in the past, this new information does help us structure a better understanding of their relationship.
"a lot of our fans have assumed "oh, that's why Reyes and Morrison hate each other," and the story that we're developing is actually, like–no, these guys loved each other–like–they're like, best war buddies." - Jeff Kaplan
We are shown in the "Junkenstein" comic that Reyes has a knack for making costumes; he is lighthearted and fun as he attends the Halloween party with a pumpkin for a head. During the Uprising event, we finally heard Reyes' voice without the gravelly undertones of Reaper as he instructs the team in Kings row, and he sounds entirely professional and competent as a leader. There is little evidence to suggest he is in any way harboring some deep hatred for Overwatch or Morrison.
So where does Moira fit into this? A brilliant, yet controversial scientist, Moira O'Deorian's research into altering human DNA was condemned by Overwatch due to her questionable ethics. Though, it seems she caught the eye of Reyes, who was now the commander of Overwatch's covert ops team, Blackwatch. He recruited Moira after seeing her potential, giving her the freedom to work without restraint, hidden in the shadows. She worked within Blackwatch, right under Overwatch's nose. It is revealed in her origins video that Moira used Reyes as a test subject. Her experiments on him gave him the ghost like, super-human abilities we know so well. However, it has been confirmed by the artist who worked on her origins video, that Gabriel isn't happy about these changes. This put to death any fan theories about Reyes' new form being Mercy's fault.
Things get more interesting when you read Reaper's bio. It states that Reaper has "fought in many armed conflicts in the last decades, showing no loyalty to any cause or organization." despite Overwatch's fall being less than a decade ago. It was confirmed that this wasn't a mistake; it was written this way on purpose. Was he operating as Reaper during his Blackwatch days? Things are slowly unraveling, allowing us to shed more light on character backgrounds, and we are able to piece together a little more of the puzzle that is Overwatch lore.