I’ve tiptoed around the Mason question when people ask, because I’d just rather people find the answer in the game. Even if it's not terribly important, or the answer is obvious. I do my best to avoid cheap cliffhangers and dramatic shock reveals, trying to make it all flow naturally from what's come before. So, while none of it's designed to be hard to figure out, I still don't just want to give it away.
It's the same reason I've avoided saying exactly when Cassie will show up, or what the secret of Ashe's photograph is. I'll get to the answer soon enough, but I'd like people to be a little surprised, even if they think they know the answer.