|| CentralAuth should globally autologin user on account creation
|| When new users want to, for example, upload photos, it's very confusing not to be automatically logged into Wikimedia Commons.
|| Enable users to change their own username if their current username is unacceptable
|| Username policy conflicts are a frequent issue that new users run into. The process for changing your name is fairly convoluted and unnecessarily bureaucratic, especially for simple cases.
|| RefToolbar on English Wikipedia needs user experience pass
|| The RefToolbar (defined in MediaWiki:RefToolbar.js←MediaWiki:Common.js/edit.js←MediaWiki:Common.js) is great, but it's not the most intuitive. It uses terms like "Templates", which newbies don't understand, and has confusing icons. It needs a holistic user experience pass and some user testing. The number of users making test edits via toolbar buttons could also be instructive, see 1 and 2.
|| MediaWiki's email notifications are not user-friendly
|| The subject lines, sender address and text of MediaWiki's email notifications are highly technical and confusing for new users. See New Editor Engagement/Email notifications for a collaborative draft spec.
|| Lack of calls to action/invitations on prominent pages.
|| Other than edit/talk buttons, AFT, and the Community Portal in the lefthand sidebar, there are no prominent links to participatory spaces nor is there an explicit invitation to become a part of the community. The site's interface has become more content-focused and less community focused over time. For example: the Main Page of English Wikipedia in 2004 devoted a third of its content to participation. Today there is nothing except a link to the little-used Community Portal.