User blog comment:Vixenblaze/COPPA?/@comment-5558012-20141026205548

It wouldn't be a COPPA violation (COPPA applies to US companies), though using the service (Wikia) is a Terms of Use violation for those under 13.
 * "You may not use the Service and may not accept the Terms of Use if you by law are barred from using the Service or accepting the Terms of Use. (emphasis mine)"
 * "Any registration by anyone under 13 is unauthorized, unlicensed and in violation of this Agreement."

Interesting, from my interpretation of the statements above, you can't be in violation of the agreement if you are not allowed to accept it. You still however can't use the service because
 * "In order to use the Service, you must accept these Terms of Use."