Vato Falman doesn't try to hide who he is. He doesn't broadcast his opinions like Jean, but he'll give them if asked. His face isn't an open book like Kain's, but it isn't closed the way Hawkeye's is when she wants it to be.
Everyone knows about his memory or they find out soon enough. He doesn't volunteer the information but he doesn't conceal it either. People worry at first, especially if they find out he's seen their personnel file. They're relieved when they find out he never uses it against them, but that eliminates the only use for his memory that they don't find boring. No one knows Vato confirmed the identity of a mass murderer's soul or recognized Father's country-wide human transmutation array. Not that they'd ever find out. That was classified Top Secret.
He keeps his uniform immaculate, his salutes precise and he always uses the correct forms of address, sir or rank. Everyone knows he's a soldier who goes by the book. They can't imagine that he might ever disobey a direct order. Or participate in a coup. Or hold a gun on the Fuhrer. That was classified Top Secret, but Vato imagines most people would have trouble believing it anyway. Sometimes he finds it hard to believe himself.
Vato takes his duty as a soldier to be prepared for combat seriously, even though he isn't rated for combat. He stays fit and never misses his weekly range practice. That doesn't give him much experience hitting moving targets, like the corpses animated with animal souls he fought when he was guarding Barry the Chopper. But he had no problem hitting the icicle that stunned Sloth. That was classified Top Secret, though, so not many people know about that.
Except for the Promised Day, Vato's had no combat experience. In all his years in the military, he's worked mostly with his mind, reading reports, writing reports. And of course, he's done a lot of mindless work as well: filing reports, copying reports. Knocking down icicles.
He doesn't like to talk about what he did on the Promised Day, though. Vato isn't ashamed of holding the gun on Bradley, but he is ashamed of his tears. And while he's not ashamed of directing the fire on the Central troops, it's something he deeply regrets, like all of the troops who fought with Briggs that day. He wouldn't have much opportunity to talk about it anyway. All of that has been classified Top Secret and few of those who witnessed it like to talk about it either.
So most people still don't know he has any combat experience. They just know he reads reports and writes reports and files reports. And has a freakishly good memory.
Vato Falman doesn't wear a mask. But most people see him through one anyway. Mustang was the first one who didn't and as he worked with the others in that office, they stopped seeing him through one as well. Later, Captain Buccaneer was another.
Vato Falman stands at Buccaneer's grave in the Soldier's Cemetery at Briggs. His uniform is freshly pressed and tears stream down his face as he clicks his heels and salutes. Then he makes a precise about face and walks away.
Won second place at FMA Fic Contest for the prompt: Masks.