First you have to install a real time hit counter like Statcounter on your blog if you do not have one already. There are various free hit counters available, including sitemeter and statcounter. Sitemeter is good for summaries. I prefer statcounter for its more detailed statistics. To see how to install a hit counter, go to How do I track visitors to my blog. When you want to track visitors to your blog, sign in to statcounter and click on "Recent pageload activities". You will be taken to a page where details of such as date, time, IP address, etc. will be shown. See screenshot below. (Click screenshot to enlarge)When you want to find out the IP address of a commentator, open the email notification for that comment. To get the timestamp, reply to the email for comment moderation.
For example, this was what I got when I reply to one of the email for comment moderation:
Sent: Thursday, June 20, 2013 3:43 AM
Subject: [the original Blogger Tips and Tricks] New comment on New: Blogger contact form gadget.
Compare it with the time shown in the visitors log. When you see a match, then very likely that is the person who made the comment. Get the IP address of that visitor from the log.
The idea for this was suggested by a comment from Dr. Lisa Cuddy.
This tip can be useful if you want to ban someone who is leaving comments you don't like as shown in this post: How to ban a person from your blog or website (click "BACK" button to get back to this site).
Books from Amazon
Publishing a Blog with Blogger: Visual QuickProject Guide
The Weblog Handbook: Practical Advice on Creating and Maintaining Your Blog
UPDATE 16 August 2008: Answer to a question in the comment about whether it is still impossible to get the commentator's IP address for Blogger: "Yes it is still not possible. You can only guess, including the country. But if your blog has low traffic, it can be a very good guess to the point of certainty. If a person comment at, say, 3pm and from morning till night, that is the only visitor to the blog, than you can say that that visitor you see in your visitor counter is the one who commented."
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