When moving a file from a file system one device to a folder on another device, Thunar crashes with *** %n in writable segment detected *** Aborted if the file name contains %n or a variation of it (like %.n etc). It seems to move the file correctly if it contains other C formatting sequences. The bug does not seem to appear in Thunar git cloned at 2011-04-29 14:06:18 UTC.
Yes, this was indeed fixed in master and the xfce-4.8 branch with commit 03dd312e157d4fa8a11d5fa402706ae5b05806fa.