It's not an extention, it's to do with setting certain group permissions. It's not an ideal system since at the moment the only people who can! authorize members are myself, Richard and Sander, i.e the forum administrators, but it's a lot better than being flooded with lots of spam, and things were getting rather out of hand there.
As to Orko's comment about forums, I pretty much do the same, though as I said I do sometimes look at people's profiles since sigs at the least often interesting to see, also I'm afraid I disagree with Orko about people putting links to their work in sigs, since it's often a good way to find things like member's walkthrus, eg, Jayde's manamon walkthrough has a link in his sig, but to each their own, that's after all what settings are for.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)