It says in the trivia section under spoilers that Malcolm never interacts with anything, however, I'm pretty sure he does move the stool in the hospital when he visits Cole.
If so, was this a mistake?
We're all in strung out shape, but stay frosty, and alert.
The trivia is wrong, Malcolm does indeed move the stool. Although it's on wheels, so it's not like picking up a book. It's not something that acknowledges or denies his existence. But the movie makes pretty clear that ghosts can interact with the real world and make objects move. Malcolm keeps opening the basement door, that's why his wife puts a desk in front of it, and Cole's grandmother keeps taking his mother's pendant. Their interactions with the real world do seem to be limited, though.
shareNot sure how the trivia is worded, but the filmmakers were careful not to have Malcolm interact with objects while normal people were watching.
For example, at the restaurant, Malcolm enters, and the chair is already pulled out so nobody surrounding the table would freak out about a table moving. Later in the film, however, Malcolm gets pissed that his wife is interacting with another man and breaks the door at the front of the store. Everyone reacts to this, and are genuinely freaked out.
Malcolm interacting with the stool wouldn't have frightened Cole, as Cole is one of the few people that can actually see him.