If you're a premium site subscriber, you get access to the feature of a journal. Essentially this feature is that you get a comment engine turned on on your user page, so you can post things for the world to see, or run a full message board.
Here's how it works:
The three settings for Journal are "Yes, Read-Only, and No".
No means the feature will not be enabled.
Read only means that only you (the person who owns the user) can post to it.
Yea means that anyone can post to it.
There are a couple caveats here. First, while the Karma system is imported to the user journals (your posting titles, and karma levels are retained from the main comment threads), they are not exported.
Since it's too easy to raise your own karma using the poster forums, no karma rating you give someone else on user forums will transfer over.
You do retain administrative access over your forum, you should be able to indefinietely rate any post in order to keep the your forum clear of whatever you consider to be dreck.
Feel feee to ask any questions in my journal here, feedback is appreciated since I'm always willing to add more features to the comments system.