When using Special:Import to do a transwiki import (e.g., from https://meta.wikimedia.org/wiki/Special:Import), if the destination title already exists, the revisions will just be "merged" (dumped) onto the same title, without warning the user. This is pretty awful. I couldn't find a bug that was tracking this issue.
Somewhat related to bug 6808.
Version: 1.21.x
Severity: normal