How many people really know what Clark Kent looks like? He lives in a world with a Lex Luthor, a Superman, various rampaging maniacs pretty much daily! How many people are going to to stop and look at Clark Kent, whether he's bumbling or not. I always liked how they put it in Batman/Superman when Supergirl got there and their looking at the Superman memorial statue, this majestic brilliant gold statue of this larger than life character with the most straight forward symbol of our nation and all the ideals that we hold near and hope to spread to world perched on his forearm and she looks at him and says "This is how they see you?", "no wonder they never figured it out".
Frankly there is no reason why Clark Kent needs to be anything but an average man. He should be clumsy, we all are. He should be goofy, we all are. He should be shy, most of us are. That doesn't mean he can't be sarcastic or funny or charming. It just means he should appear normal. Yeah he puts on the glasses as a distracting feature, he changes his body language, he weakens his voice. He does after all work in the bull pen at one of the top newspapers in the country, not only that but he's one of the star reporters of that paper. Those people are the professionals at sniffing out the news but even they seem him as if he were a god. He is omnipresent to them. They have no reason to suspect he is ever anyone but Superman. They trust him completely. The believe in him. To them, to everyone, Superman could never be Clark Kent.