The main features that LJ supports that WP is (or was) “missing” seem to be:

• Robust permissions (create a group of people, grant them access to view a post, but no one else, etc)
• Support for integrated “metadata” on posts such as Current Music, Current Mood, etc
• Reply to comments directly via the notification emails you get
• Threaded comments
• Userpics

Some of these features (threaded comments, userpics) are already at least partially supported in WP, and there are ways of supporting the others that could perhaps be rolled into a single plugin (which I’m calling “LiveJournalish” for now).

• Customize the Post UI to include specific fields for music/mood, but save them as normal Custom Fields (postmeta).
• Add a filter to the_content that appends a specific set of Custom Field values if they are set (or just make them more readily available via a different template tag)
• Use IntenseDebate, which allows you to reply to comments via email, or perhaps roll up something new that includes the comment posting form in an HTML version of the email?
• Threaded comments are available in core as of WP 2.7

This leaves the permissions system as being the main thing missing, and I believe that’s going to be addressed in the near future. WP already has a Roles and Capabilities system, it just needs to be extended to be more robust as far as being used for controlling permissions. Some of the DiSo work being done also requires this, so now we have another use-case for it.

Just some random ideas, if you have another other suggestions feel free to put them in the comments.

As it turns out, it’s been quite a project. LiveJournal’s API is, shall we say, “challenging” to work with, and the sheer size of Guav’s journal (over 3,700 posts and nearly 200,000 comments) meant that I kept running into time, memory and database limits that would crash the importer. After a lot of back and forth with Guav though, I’m happy to present the new importer (find it under Tools > Import > LiveJournal), sporting the following features:

• Just enter your LiveJournal username and password and you’re ready to go
• Via the API, it connects directly to LiveJournal and imports all of your posts,
  • Posts marked as “Friends Only” are assigned a password within WordPress,
  • Posts marked as “Private (you only)” are marked as Private within WordPress, which means that only authors on your new blog can read them,
  • lj-cut tags are converted to the WordPress equivalent, the <! — more — > tag,
  • lj-user tags are converted to normal links, and have class=”lj-user” attached to them to make it easier to style them if you like,
  • Tags are imported properly,
  • If you closed the comments on a post in LiveJournal, then they’ll be closed in WordPress as well,
  • Lots of the “meta” information related to posts is also imported using WordPress’ Custom Fields feature. You could then use these values to reproduce some of LiveJournal’s functionality within your new theme if you like. The fields imported are:
    • If your post contains adult content (lj_adult_content),
    • Your current co-ordinates and location (lj_current_coords and lj_current_location),
    • Your current mood (lj_current_mood),
    • Current music (lj_current_music),
    • Your userpic keyword (lj_picture_keyword)
• Next up, all of your comments are also imported,
  • Threading is preserved, so replies to other comments show up successfully (provided you enable that feature in WordPress),
  • The “subject” of each comment is included as the first line of the comment itself, because WordPress doesn’t have a comment title/subject value,
  • LiveJournal users get links back to their LiveJournals,
  • Your own comments are linked to your WordPress account, and are linked back to your new WordPress blog,
  • Anonymous users are labeled as “Anonymous”,
  • “Screened” comments on LiveJournal are imported as “Unapproved” within WordPress, so you can decide what to do with them

So there you have it, a brand new, shiny LiveJournal importer. This should be bundled with the 2.8 release of WordPress (it’s available right now on WordPress.com), and will be available for everyone. As I mentioned, it’s been tested with one single, very large blog (and a few smaller test ones), but if you find anything wrong with it, please file a bug on the WordPress Trac!

Huge thanks again to Guav for helping with the testing of this thing (maybe now he can migrate over to WordPress as well)!

I’m now in touch with one of their people who’s handling the actual implementation of their APIs, so hopefully I’ll be able to work out what’s going on and add LJ support to the code library soon. At the moment, my WSSE authentication is failing on the second request to their API, even though it’s working on the first one… curious.