CaptFrost

From a lore perspective, if you choose Nate, he might already have power armor training from his back history. "At some point before 2077, Nate served in the US Army during the Sino-American War, in the 108th Infantry Battalion's 2nd Regiment." (Source: http://fallout.wikia.com/wiki/Nate ) This could explain the lack of needing any power armor training in the game. It would put Nora at a disadvantage with her non-military background as a lawyer, so to make choosing one over the other have no significant difference in mechanics they just took out needing the training at all. Here's how I see it: The intro movie centers on Nate's military background and even shows Nate on patrol with a squad member who is wearing T-45d. It makes total and absolute sense that he'd know how to use and perform field service on power armor, even if he wasn't issued his own suit. It's like having a light machinegun in the squad. Not everybody's issued one, but everybody knows how to pick it up and use it or clear a jam or what have you if the need arises. There's absolutely no way Nate spends day in, day out in a unit that has power armor in service and doesn't know quite a bit about it. As for Nora... a lady friend of mine is a lawyer. That takes a certain personality type. Trust me, if it was real life and I was power armor trained, unless it was classified information and I couldn't talk, she'd have been curious enough and asked enough questions to have the basics down just being my friend, nevermind my wife. Again, makes total sense to me that Nora would know how to use it, being married to Nate. What doesn't make sense to me is Random Wastelander B being able to use it as long as there's a fusion core installed.