William Wilson takes an up-close-and-personal look at his double’s features while at Dr. Bransby’s school. And it is not a pleasant experience. “When the bright rays fell vividly upon the sleeper, and my eyes, at the same moment, upon his countenance. I looked;—and a numbness, an iciness of feeling instantly pervaded my frame,” he tells us (26). This is the last time he gets a good look at his nemesis’s features. (Nemesis means enemy.) For the rest of the text, William Wilson #2 lurks in the shadows or hides his face.
When he surfaces at Eton, the narrator writes that “[because of] the faint light […], the features of his face I could not distinguish” (29). At Oxford, the lights magically go out when the doppelganger enters the room. At the masquerade, the double’s face is hidden by a mask of black silk. You get the picture.
If you buy the theory that the doppelganger is a product of the narrator’s overactive imagination, then his face is hidden because William subconsciously wants it to be hidden. This makes sense; he was horrified the last time he looked at his double up close – why would he want to do it again? For one reason or another, William’s subconscious doesn’t want his conscious self to know that his doppelganger is really his alter ego.