Ok, how many hops away does traceroute tell you the 216.23.15.143 addr is? and why is
REMOTE_ADDR is set to 216.23.15.143 and
SERVER_ADDR is set to 216.23.15.143 the same?
(sorry I don't know this logging as I really don't do that much webserver stuff)

I would suggest sniffing the packets as they hit your web server and finding out what is going on.

"Nothing is sure but death and taxes" I say combine the two and its death to all taxes!