Board Thread:Technical Updates/@comment-126761-20180124213059/@comment-34039680-20180207165311

I believe that Wikia has a central database for all users. No long time ago, Special:ListUsers was displaying all Wikia users, not just the "local" ones.

This explains why you don't have to register to every wiki you want to edit, but you use an only one wikia user for all the wikis.