access_log format $remote_user anonymous question

Wed Sep 21 19:30:31 UTC 2016

So in my access logs all my other logs the $remote_user is empty.

But for only this one single IP that keeps making requests the $remote_user
has a value.

CF-Real-IP: 176.57.129.88 - CF-Server: 10.108.22.151 - anonymous
[21/Sep/2016:18:54:52 +0100]  "GET
/media/files/29/96/2b/701f56b345ce531192645ddb532a8fd7.mp4 HTTP/1.1"
Status:503 206 "http://www.networkflare.com/" "Mozilla/5.0 (;FW 2.0.7070.p;
Windows NT 6.1; Trident/7.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729;
.NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; Tablet PC 2.0;
rv:11.0) like Gecko"

Why is the $remote_user value on this person anonymous where everyone else
it is empty ?

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,269734,269734#msg-269734