Hi there. The Editor Engagement Experiments team wants to improve the account creation user experience[1].
One simple change is after someone successfully creates an account, instead of showing 'Login successful', make the page show 'Welcome, NewUser'. We filed a bug[2] and the change is mostly-merged (thanks Nikerabbit and IAlex) and should roll out with 1.21wmf5 over the next two weeks.
This means the existing welcomecreation message splits into new welcomeuser and welcomecreation-msg messages. If a wiki has customized its MediaWiki:welcomecreation message then that will probably need adjustment.
I thought about removing or replacing welcomecreation but the extensions ApiSignup and SpecialUserSignup (unused by WMF) and ./tests/parser/preprocess/ all refer to it. Do developers usually introduce a new message then obsolete the old one, or cut over in one commit?
For your information, the E3 team has more substantial changes to user login, account creation, and onboarding (welcoming users after account creation) in development. I'll keep i18n people informed; I hope this is the right list for the changes. I figure any communication is better than throwing code onto 863 wikis and letting people figure it out :-)
[1] https://www.mediawiki.org/wiki/Editor_engagement_experiments#Projects [2] https://bugzilla.wikimedia.org/show_bug.cgi?id=42215
-- =S Page software engineer on E3