1) That's a language string that is used to show that. While I'm not sure why it's showing up 2 times (it should only happen 1 time), you can easily remove it altogether. To do so, edit the /language/en_gb/en_gb.com_jfbconnect.ini and find the "COM_JFBCONNECT_MAP_USER_SUCCESS" string. It should look like:
COM_JFBCONNECT_MAP_USER_SUCCESS="%s profile successfully connected."
Update that to:
COM_JFBCONNECT_MAP_USER_SUCCESS=""
2) That method works with our SCLogin module whenever you are using the User Menu option. You can see an example in the top right of our page where the drop-down has a Logout button that directly logs you out. If you're trying to use that menu item anywhere else, the logout button won't work. It's only our SCLogin module that can correctly detect the sclogout link and turn it into a direct logout link.
I hope that helps,
Alex
Login / logout questions
