I am running WikiMedia on nginx (CentOS 6.3 is the OS if it matters) and using CloudFlare to protect the site. The nameservers are currently pointed to CloudFlare. WikiMedia displays CloudFlare's IP address rather than the client's IP address when editing a page.
For an example, see http://bit.ly/12ixWdR. You will notice the IP address is always 126.96.36.199 (or a CloudFlare IP address) when changing an article which is CloudFlare. It should report the user's external ISP IP address rather than CloudFlare's. Otherwise, you won't know who edited what.