I've disabled guest posting for the most popular sections in an effort to hopefully reduce spam a bit. I'm spending too much time removing individual spam posts. There should be a better forum (and dedicated site) for Sculptris when it's released.
I don't really know what you mean. The administation area of this forum is rather convoluted, so it's hard to get an overview of relevant settings. From what I can tell though, you should be able to do most things you'd expect when you have registered as a user. The most important thing is that you can post/reply in existing threads though, and I take it that works? Or does it only work for the guest-enabled threads like this one?
I cannot upload a wip as there is no "new thread" button under the wip section of the Sculptris forum. I am a registered user of the forum so starting a new thread for uploading a wip should be should be enabled. I can only reply in all forum sections but not start a new thread in any except the main sculptris fourm which would add to the list you started which is something I do not think you would want me to do...
Here is what I see on my end under the wip section of the forum but is true in all forum sections
search, bookmark, reply, send topic to friend, print
Fletch, who started the WIPs thread, didn't actually intend to do that as he later realized there was another thread for posting sculpt pictures (Sculpture showcase).
My idea was that anyone who had made something they wanted to show off would post a reply in the showcase thread. If you plan on uploading a lot of separate steps for a single model, you can do that in a new thread under the main Sculptris board, if you want to.
There's not enough activity on the forum to require any complex structure right now.