Here's an example.
This is from the novel 1Q87 by Haruki Murakami.
Just before noon, Tengo put on a raincoat and hat and was headed out to the local market when he noticed a brown padded envelope in his mailbox.
I would have written the first part like this: Just before noon, Tengo put on a raincoat and hat, and was headed out ... So the reader doesn't think for a second that the list continues after hat.
Is this a grammatical rule? Or maybe that comma is unnecessary?