There seem to be an awful lot of comic strip characters without mouths. When I first saw Dilbert, I thought of the Harlan Ellison story “I Have no Mouth, and I Must Scream”. It seemed so appropriate. They had to give him a mouth for the animated series, and it looked so wrong.
But he’s just one in a long series of such characters
Henry
The Little King (who often seemed to have nothing under that moustache) Hello Kitty
The “mascot” for the defunct Washington DC The Game Room The Aliens who must Register in January of Each Year on those old, weird, limited-animation public service commercials.
This reminds me of that issue of She-Hulk where she fought Xemnu the Titan. The story was called “I Have No Mouth and I Am Mean”. (I think Xemnu communicated telepathically though).
They don’t have eyes either. They’re hidden by glasses.
I think the absence of a mouth kind of reflects the futility Dilbert has to endure on a daily basis. Instead of lashing out in rage, or crying, or fretting, he’s maintaining a calm, stolid demeanor that’s expressionless and incorruptible. Occasionally the eyebrows will cross down in anger, but he’s not going to lose the iciness in his face or the bastards will win.
In Dogbert’s case, the nonmouth reflects his complete disregard for human intelligence as he dispassionately seeks to exploit it.
I dunno, I think that little black circle is his mouth (which is always open, since we never seem him when he’s not speaking). But it could be his nose, I suppose. In any event, he’s certainly facially-deficient.
George Herriman didn’t show mouths in most of his Krazy Kat Karacters: Krazy, Ignatz, and Offissa Pup didn’t usually have them. Since Krazy Kat is the greatest of all comic strips, it’s probably where some of the others got the idea.