Doesn't look like you have any other real options. Looks like a pretty bare-bones "forum" and there probably aren't any controls, settings, etc. for a user to create. It may be so bare-bones that it doesn't actually protect any of your input or info from anyone. I doubt it even uses 'cookies'. It may be relying on what your computer sends on any call for a page. And that info may be different when you use private browsing. The part that identifies the browser (Safari, Foxfire, Opera, whatever Windows now has, etc.) probably explains why you still need to log in from FF.
Your best hope is that the database containing your name and any other personal info is well encrypted. Just don't post personal info that could ever be used to lead back to you. Of course, it is more and more likely that any two pieces of personal info can eventually be traced back to you and most of your other details. The web has replaced the physical bulletin boards we used to see at the local grocery store... the big difference is it won't be your friends who will see and be collecting that info. :eek: It's a Jungle Out There! (https://www.youtube.com/watch?v=xBdF3E2NVI8)