Title: Why can't I post anonymous comments? What is an Open Proxy?
An Open Proxy is an unrestricted point of access to the internet. Because they are unrestricted, Open Proxies are frequently used by spammers, who have difficulty gaining access to more controlled access points. In order to protect the site and its users from comment spam LiveJournal disallows any anonymous comments which are received from Open Proxies. Administrators are aware that this can block genuine comments as well as spam and work to refine the system continues but there are no plans for change in the near future.
IP addresses are identified as Open Proxies based on a publicly available register, which is frequently being updated. This register is not managed by LiveJournal but externally by http://www.spamhaus.org. To have your IP address unblocked you will need to contact your ISP to inform them of the situation. They can then discover why the IP address has been blocked and start the process of having it removed from the blacklist if possible.
If you are unable to avoid making use of an Open Proxy when connecting to the internet, you may wish to consider creating an account for use when commenting. Please see http://www.livejournal.com/support/faqbrowse.bml?faqid=104 for assistance with creating an account.
Some technical people and probably rah and mark definitely need to look at this to check for accuracy but yeah. First draft. Anyway, I'll pipe down now.