Due to a recent incident where a community member received unwanted, harrassing anonymous comments, anonymous commenting is currently disabled for this community. (This is the sort of thing we would otherwise ban a member for, but you can't ban IP addresses.)
Commenting is currently open to all registered LiveJournal users, whether they are members of the community or not. Users logging in via Facebook can also comment, as can users logging in via Twitter or OpenID as long as they have associated an email address with their login and have validated that address.
If there is a comment you would like to leave but would like to do so anonymously, I would suggest that you create a new LiveJournal account for this purpose; if you do not wish to do so, you may also contact a maintainer (see contact info on the community's profile) and explain the situation, and a maintainer may choose to post the comment in your name.
We may revisit this decision to disable anonymous commenting in the future; if you have an opinion one way or another, please feel free to let a maintainer know (now or later). (You may also comment on this entry for this if you'd like.)