We are using SPO and encountered this issue when trying to logout using Yahoo. The signout happens fine with all browsers, except for IE. Somehow, the cookie still persists for the user and the next time, the user can login without being challenged. We looked through fiddler and it seems that ADFS doesn't like the cookie and terminates the process abruptly.
Please note that document.execCommand('ClearAuthenticationCache') works for all browsers except IE. For IE we need to close the browser to terminate the session. This is not consistent with our requirement, where it should take us back to the login page as it's doing for all other browsers.
SharePoint Architect