Actually, a reverse blade sword may be just what it sounds like, but I am not sure what it sounds like. (By your later explanation, I would guess that it is a blade that has an single edge on the opposite side from where one would expect it. (My first thought when I saw the thread title was a blade extending back from the hilts toward the wielder, but I dismissed that impression as unlikely.)
If I have understood your question, the answer would be “Yes” a reversed blade sword can still kill. (People get killed by fireplace pokers or golf irons every once in a while.) A sufficiently strong blade could easily deliver a blow that would crush a skull. (It could also break the bones in an arm or the rib cage after which internal bleeding could kill the victim.)
On the other hand, if all strikes were delivered with the flat of the blade, the energy would be dissipated, reducing the possibility of a crushing stroke. (By the way, even armor would not necessarily prevent death from a reversed blade. Hammers and maces were used extensively after plate armor was developed specifically because they could be used to crush an armored helmet into the head of an opponent. A katana would not have the concentrated weight of a mace or hammer at the point of impact, but it is still possible to kill in that way against leather, mail, or less-than-plate armor.)
One presumes that your hero would wield his sword in a way to avoid crushing injuries and that the reversed blade was simply insurance to prevent an opponent from accidentally slashing hiself open.