There seems to be a rather serious bug in the global rename user facility that allows destruction of revisions making them no longer available for admins to retrieve. See https://en.wikipedia.org/wiki/Wikipedia:Bureaucrats%27_noticeboard#Rather_serious_rename_bug for more details [ https://en.wikipedia.org/w/index.php?title=Wikipedia:Bureaucrats%27_noticeboard&oldid=659873109 ]
I have replicated the bug and destroyed revision 659870568 https://en.wikipedia.org/w/index.php?title=User:Test_account_042915_newname&oldid=659870568 https://en.wikipedia.org/w/index.php?title=User:Test_account_042915_newname&action=history
1. User moves their userpage to a desired new name
2. User later requests rename
3. Rename ends up moving the user-created redirect over the proper target and old revisions are nowhere to be found.
Expected behaviour: Old revisions would be available in the deleted edits.