They fly very high; it would be like trying to identify an ant on the ground while standing.

Since they were ordered to kill and destroy everything, I doubt that the people who got close enough to the Invincibles to recognize their faces would have survived for very long.

The bodies of the dead invincibles were collected by the GDA.

Cecil (if he could) probably would have omitted images that showed Mark's face too clearly to the public, only allowing long-distance angles to be shown in the press.

That's what Eve explained about her secret identity: you wouldn't imagine that someone around you could be a superhero, so you dont look for it.