MirrorTools needs to add flags to show which revisions originated on the local wiki and which originated on a remote wiki. Functions that might need hooks added:
*EnhancedChangesList::recentChangesBlockGroup()
*OldChangesList::recentChangesLine()
*HistoryPager::historyLine()
*DifferenceEngine::showDiffPage()
...among others. Maybe alternatively, we can fix bug T59490 and come up with a solution that involves listing the origin wiki of revisions (rather than just displaying a one-letter flag, e.g. "W" for Wikimedia, etc.)