What is Comment IP Logging? What do you mean, "this user is logging my IP address"?
As an anti-abuse/harassment feature, LiveJournal owners can now choose to log the IP addresses of users that comment in their journal. The levels
An IP address is the numerical equivalent of a domain name; the unique address of a computer connected to the internet. Most providers assign IP numbers on a random basis from their set of addresses upon connection; most likely, if you have a static IP address (which is always the same), you already know and have probably paid a premium for that service. Domain name servers convert a domain name, such as livejournal.com, to an IP address, such as 126.96.36.199.
The IP address is not harmful, and does not point directly to your home or telephone number. It will, however, allow a user to identify your Internet Provider and by comparing logs and timestamps, the internet provider should be able to connect a particular posting to your account. You can find out who the Internet Provider is and inform the Internet Provider's abuse department of the transaction.
There are official sites that allow you to query the IP address:
American Registry Internet Numbers (ARIN) http://www.arin.net/whois
Réseaux IP Européens) (RIPE) http://www.ripe.net/ripencc/pub-services/db/whois/whois.html
Asia Pacific Network Information Centre (APNIC) http://www.apnic.net/search/index.html
The only people who can see the logged IP numbers are the owners of the journals in which the comments appear (or the owners of entries in Community Journals to which comments have been made), and the owner must be logged in to be able to see them.
You can log in at http://www.livejournal.com/login.bml to see the numbers, which appear to the right of the timestamp on the comment in question. The IP addresses will only appear at the time when IP Logging was enabled and does not retroactively affect previous comments left by other users.
update (2002-01-21): Added the European and Asian Pacific counterparts to ARIN and some typo changes.
update (2002-01-23): Rephrased the first sentence and struck out the last line.