  We consider the N=1 supersymmetric kink on a circle, i.e., on a finite
interval with boundary or transition conditions which are locally invisible.
For Majorana fermions, the single-particle Dirac Hamiltonian as a differential
operator obeys simultaneously the three discrete symmetries of charge
conjugation, parity, and time reversal. However, no single locally invisible
transition condition can satisfy all three. When calculating sums over
zero-point energies by mode number regularization, this gives a new rationale
for a previous suggestion that one has to average over different choices of
boundary conditions, such that for the combined set all three symmetries are
obeyed. In particular it is shown that for twisted periodic or twisted
antiperiodic boundary conditions separately both parity and time reversal are
violated in the kink sector, as manifested by a delocalized momentum that
cancels only in the average.
