This is a bit strange, blogger.com is using google-analytics to track users on the "Post a Comment On" pages. I would presume they have the log-files anyway, so the only reason that comes to my mind, why they do this is because google-analytics has better analysis -tools than they have.
But still, what is strange that they have such an interest in who leaves comments. (They don't seem to care as much about who is visiting the blogs hosted by them).
I posted it here, let's see if someone comes up with an answer.