User blog comment:MisterWoodhouse/Social Activity, the 2010 Editor, and Unpausing Migrations/@comment-43528456-20200922205333/@comment-3218221-20200923004657

Legacy wikis are simply wikis that haven't been migrated to UCP. They're based on MediaWiki V1.19 (heavily customized), whereas UCP is 'upgrading' to MediaWiki V1.33).

You can't create legacy wikis: all wikis created after March 11, 2020] are UCP Wikis. However, you can of course still edit existing legacy wikis; 3/4 of the wikis I admin are legacies, and the 4th was migrated to UCP in August.

The Chat feature can still be enabled/disabled on legacy wikis (I just tried on one of the aforementioned three), but will go away once the wiki is migrated to UCP.

I see you edit on "Battle for Dream Island Wiki," which is a legacy wiki w/chat enabled scheduled for migration soon. Again, your chat room will cease to be when your wiki ceases to be legacy.