en.wiktionary:
If you edit a section of a page and an edit conflict occurs, the bottom textarea will only contain the section you edited.
It used to show the entire page in your textbox, and not just the section you edited. With the way it is now, we've had it happen very often that users inadvertently deleted the entire page like this.
Example of accidential delete due to this: https://en.wiktionary.org/w/index.php?title=Wiktionary:Requests_for_deletion&diff=18610741&oldid=18610739
Problem forwarded from https://en.wikipedia.org/wiki/Wikipedia:Village_pump_%28technical%29#Problem_with_edit_conflicts
https://commons.wikimedia.org/wiki/Commons:Village_pump#Edit_conflict_issues
Version: 1.21.x
Severity: major
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=25681