Per the discussion among Editing-team today, we'd like to enable the DiscussionTools Usability Improvements on MediaWiki.org for everyone by default. This will affect relatively few pages, as most discussions on the project use Flow. It will in particular affect https://www.mediawiki.org/wiki/Talk:Talk_pages_project/Usability (the talk page about this very feature), which we want in order to make it easier to discuss the feature in vivo.
All other DiscussionTools feature are already enabled since T302256.