Would be a nice feature to have Special:FileDuplicateSearch also search the checksum for deleted files to detect re-upload of previously-deleted files. One will be able to detect repetitive copyvio or other problematic files uploads under different names. Currently, one must search through their deletion log for blue links and check them (which matches only if they reupload under the same name). This would allow much easier detection of repeated copyvio uploads under any name.
T16417: Generate upload log entry when duplicate file uploaded