I didn't see a random salt per user in the example. There really shouldn't need to be a random salt. The point is anonymity, so leave anything that ties it to the user at all out. There's no need to prevent sensitive information leaking if there's no sensitive information. A crypt on the session ID and the root node ID should be plenty to assure separation of credit for the thread, so why include anything else in a publicly displayed string?
This all kind of assumes the idea would be picked up anyway, which is not by any means a foregone conclusion. It's all just painting a bike shed that may never be assembled.
The level of information trusted to the site admins shouldn't by default be trusted to everyone. Don't assume that giving up IP information to the public would be okay with everyone just because it's okay with you. Apparently you're forgetting (or simply not aware, but that's doubtful) of the issues of stalking and harassment other people have had to deal with.