  There has been a corporative absence of understanding of Hall anomaly data in
the mixed state in terms of vortex many-body effect and pinning, because of the
dominant theoretical influence. Now D'Anna et al. [ Phys. Rev. Lett. 81, 2530
(1998) (cond-mat/9808164)] are brave enough to announce the prominent role
played by vortex many-body effect and pinning in their interpretation of their
own data. Here I wish to point out: (1) Indeed the data of D'Anna et al. can be
explained within an existing Hall anomaly theory based on vortex many-body
considerations; (2) It is not surprising that their data are not consistent
with available microscopic Hall anomaly theories, because those theories are
mathematically incorrect; and (3) The courage of D'Anna et al. should be
appreciated.
