Hello,
Although this is minor issue, it can affect user experience, so I thought you might want to fix it. RB 6.0.1.
Ensure you are logged in and then click "Log out" popup menu item. You will be redirected to "Logged out" page (/account/logout/).
Now click "Log in" button. You will be redirected to "Log In" page (note, URL will be /account/login/?next=/account/logout/).
Log in and you will be redirected to /account/logout/ which effectively logs you out (by setting 'Set-Cookie: rbsessionid=""' I guess).
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Regards,
Mikalai Ananenka