I've added a reply button to the bottom of threads, hope that makes it more obvious where you need to click. Should I also add a reply button to the right side of the header, where the [edit] link is on normal headers?
But yes, add a button there too. Although you won't see that if you're going via the "new messages" tab, as I am mostly. I've still yet to get used to reading this on an actual thread or page yet!