What is Comment IP Logging? What do you mean, "this user is logging my IP address"?
As an anti-abuse/harassment feature, InsaneJournal account holders can choose to log the IP addresses of users who comment in their journals. Logging can be enabled for "Anonymous posters only" or "Always", or it can be left disabled by choosing "No". You can select the option you want at http://www.insanejournal.com/editinfo.bml under InsaneJournal Options.
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 insanejournal.com, to an IP address, such as 126.96.36.199.
The IP address is not harmful, and does not point directly to the poster's home or telephone number. It will, however, allow the recipient of a comment to identify the poster's Internet service provider (ISP). By comparing logs and timestamps, the ISP may be able to determine from where the comment was posted.
There are official "Whois" sites which allow you to query the IP address. To find one of these, perform a query for "whois database search" in your favorite search engine.
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). The owner must be logged in (http://www.insanejournal.com/login.bml) to see the IP numbers, which appear to the right of the timestamp on the comment in question.
IP addresses are recorded only while logging is enabled. You cannot retroactively view IP addresses of users who left comments while logging was turned off.