After entirely too long a hiatus, the library is back online. The reason for the site going away in the first place was a seemingly endless army of problems upgrading over nine major versions of the wiki application, Wagn. After getting it done, it was compounded by a database error latent for two years, my own stupidity in nuking my CSS customizations without actually ditching them (which didn't work), and a distro migration on my host.
November 28, 2014 - The Thornton 2 Library is back
Also, anonymous users can create +discussion cards (also available from the gear menu, "discuss" item). Previously, the +discussion card had to exist already (I had to manually add it) before anonymous users could leave comments.