"I am logged into an application using one SSO username, but I want to be logged into a different SSO account. However, when I log out and back in, it logs me in as the same user without giving me a sign-in prompt."
This is because you still have a global single-sign-on (SSO) session. To completely log out of your SSO account, browse to https://logout.linuxfoundation.org/ After that, you should see a full log-in prompt again which will allow you to log in with a different username or linked social identity.
**Please also note that using the above logout link will not destroy sessions in other web applications you may have previously logged into with your last SSO session - so you may be logged into different SSO identities on different sites.