even stranger - the rules have changed again! - even today's paper contradicts itself...
in today's Killer we have
Within each dotted-line "shape", a digit CAN be repeated if the normal row column and 3x3 box rules are not broken.
Yet in the full page article on p20 "since numbers cannot be repeated within a single sum box"... and lots of rules implying the same (eg 1,2 and 3 as only candidates in a 3 square cage.
I suspect that the CANNOT rule is the correct one - has anyone ever seen a Killer Sudoku that breaks the rule? You could for example have a cage containing 4,1,1 if it was placed on the junction of 3 3x3 boxes...