Well this is just phase 1 of the new and improved GC. With a new GC there are new features.
1. Bolded thread titles means you have NOT read that thread. Not bolded thread titles means you have read the thread.
2. At the very bottom of the page, you can see related threads. In other words, GC has done a preliminary search on your behalf.
3. To created a new thread, select forum tools at the top right of the screen.
4. If you have posted in a thread, you will see an arrow.
5. No more member, junior member or senior member, you are all now registered users.
ETA:
I corrected #1's feature note. Oops.
6. At this point the "log in invisible" feature is not on GC, but stay tuned for it to be returned to us.