I just tried a typical registration flow on riot.im/app - signing up as matthewtest17. I copied the verification link from my mail client into the browser, did the captcha, clicked the T&Cs, and then got logged in as a Guest rather than matthewtest17. This triggered two weird errors: "To do this action, you must register" (despite me having registered), and then a warning that I was logged in a guest whilst trying to do behaviour as a registered user. I then explicitly chose login from the TopLeftMenu to re-login as matthewtest17. :-/