Do you have your Gmail account enabled as an external account in the left pane under "Add mail account"? If so, on the Inbox page click on the gear icon in the upper right corner, then on Settings>>>>>accounts. You should see the Gmail account. Look to the far right and you will see a trashcan icon. Click on it to delete the account.
The account has been deleted. I have shut down email and restarted. Message returns. So no my question is not answered.
Did you only get out of the email, or did you sign out of the Comcast account? Sometimes you need to do that in order for the change to "take".