Hello!
Global user pages have now been deployed to all public wikis for users with CentralAuth accounts. Documentation on the feature is available at mediawiki.org[1], and if you notice any bugs please file them in Phabricator[2].
Thanks to all the people who helped with the creation and deployment (incomplete, and in no particular order): Jack Phoenix & ShoutWiki, Isarra, MZMcBride, Nemo, Quiddity, Aaron S, Matt F, James F, and everyone who helped with testing it while it was in beta.
[1] https://www.mediawiki.org/wiki/Help:Extension:GlobalUserPage [2] https://phabricator.wikimedia.org/maniphest/task/create/?projects=PHID-PROJ-...