Ok, this bug is a little bit tricky to reproduce. Sometimes I have slow internet connections and my laptop is rather old. The bug I want to report happens when I click the 'Watch Thread' link on top of a thread while the site and JS are not fully loaded. I get to the non-JS fallback confirm page. But from here with enabled JS, the redirect to the thread don't work because ajax does its job in background. You can also reproduce this scenario if you disable JS before clicking 'Watch thread' and on the confirm page enable it.