In response to the post about Steve’s helmet being protection and Bucky’s mask being a muzzle, I thought I’d point out something else.
Steve is able to remove his “mask”. He makes a point of it at the very beginning of the movie when a villain pretty much goads him about fighting as just a man. Steve can remove his persona whenever he wants. He chooses to repeatedly. Yes, he’s Captain America, but first and foremost he’s Steve Rogers. He spends a good chunk of this movie fighting both as Steve Rogers and as Captain America without the mask. He REPEATEDLY removes the helmet mask, even when he might need it, to remind people he’s STEVE.
Bucky doesn’t have that kind of autonomy. His muzzle mask remains firmly in place until Steve physically removes it. Bucky never does. He has nothing to remind anyone that he IS. He’s the Winter Soldier, not Bucky. He’s bled so much into that persona that he doesn’t know Bucky even exists. He’s no longer wearing the mask, the mask is wearing him. It isn’t until Steve rips the mask off that you suddenly see Bucky start to get some of his own personality back. The second the muzzle is removed, the first thing Bucky says is actually very very human. “Who the hell is Bucky?” He shouldn’t care who Bucky is, yet he’s curious enough to ask. He even words it with some very human sass to it. He doesn’t just use the minimal wording of “Who is Bucky?”, he throws that “hell” in there. The “what the hell are you on, dude” is implied in the comment. It’s like the minute his mask goes, some of Bucky comes back. And once the mask is off, it’s never replaced. The genie’s out of the bottle at that point. Bucky is starting to separate himself from his persona no matter how much they torture him or brain wipe him. Even after it’s removed, it’s never implied that Bucky has the autonomy to choose whether to put the mask back on. People decide for him. But the initial split suddenly shows the growing divide between Bucky Barnes and the Winter Soldier.
CA:WS is all about freedom of choice. You choose to fight, choose what you believe, choose who you are. Steve is the embodiment of that and he shows it by sliding between Steve and Captain America. Bucky is the antithesis of freedom. He can’t choose who he is until the very end.