  The Letter is analyzing bulk spin (moment) currents and spin (moment)
accumulation at edges of a 2D topological insulator taking into account
reflection from edges. Accumulation occurs only at edge states, which
distinguish topological insulators from conventional ones. The band continuum
can support the transverse bulk spin (moment) current, but it does not governed
by the topological Chern number and may exist in a conventional insulator.
There is no edge accumulation related with bulk currents.
