For a recent support request, I wanted to explain the different security level settings for who can send you private messages, and looked for an appropriate FAQ, but didn't find one.
FAQ 270 mentions where to change this setting but doesn't explain what they do -- compare FAQ 23 on comment settings which is more explicit.
How about something along these lines:
Your Inbox is also where you send and receive private messages from other LiveJournal users. Writing a new message to another LiveJournal user is as simple as clicking the "New Message" button and filling out the form.
You can restrict who can send you messages at the Edit Profile page (Contact Info > LJ User Messaging). The possible options for this setting are:
- Registered Users: allows any logged-in user to contact you this way
- Friends Only: Excludes everyone but your Friends
- Only Mutual Friends: Excludes everyone but those Friends of yours who also list you as a Friend
- Nobody: does not allow anybody to contact you by sending a private message to your Inbox
- It is also possible to ban individual users from sending you private messages by banning them from commenting in your LiveJournal.
Your account type [...]