Don't use the back button, click on the forum that you are browsing in itself, up at the top in the "header" below the banner, and it will show you a current view of the forum not the cached view. So in this thread for example, you would respond and then click on "site suggestions and feeback".
Some of the cookies are definitely set to a quick expire because the site used to remember me, and now it only remembers me for about an hour or so, even if I click remember me.