I guess I am automatically member of all the other Wiki-sites, ain't I? As far as I can check, my name appears when logging in on Wikipedia and on the following website: commons, wikibooks, wikiquotes, wikiversity, mediawiki, wikivoyage, wikimedia, wikispieces. Other websites I did not check yet. Nonetheless most of these I never use. The only website that does not show my account name in the right upper corner is Wikidata. When I want to log in on wikidata it automatically refreshes and then claims the following: "You are centrally logged in. Reload the page to apply your user settings." I just tried to log out and log in on Wikibooks and did the same on Wikimedia Commons.. It both worked fine.