Repro Steps:
1) Move an existing file to a new path.
2) Make small non-whitespace modifications to that file
3) Arc Diff
Result: "This file was changed only by adding or removing whitespace" shield is applied to the origin of the moved file, immediately after yellow bar stating: "This file was moved to ..." It seems in this case no shield should be applied - as the contents of the new file differ from the old contents and the old file has been deleted.