Would be harder to conceal his social manners/standing and general attitude than his personnal appearance, since I really doubt that everyone care enough about the imperium to recognize him at first glance.
"Hey, doesn`t that guy over there looks like the emperor?
- Dunno, haven't seen him yet, I don't follow Interstellar Politic that much
- Look, I've got a photo of him on my handcomp
- Well, yeah, he looks kindof like him... but so does my stepfather
- Oh well.. there`s bound to be some look-alike in the Imperium"