  The low-temperature thermal conductivity \kappa_0/T of d-wave superconductors
is generally thought to attain a "universal" value independent of disorder at
sufficiently low temperatures, providing an important measure of the magnitude
of the gap slope near its nodes. We discuss situations in which this inference
can break down because of competing order, and quasiparticle localization.
Specifically, we study an inhomogeneous BCS mean field model with electronic
correlations included via a Hartree approximation for the Hubbard interaction,
and show that the suppression of \kappa_0/T by localization effects can be
strongly enhanced by magnetic moment formation around potential scatterers.
