  Measurements of thermal conductivity ($\kappa$) versus temperature and doping
for several cuprate superconductors are discussed. Suppressed values of the
normal-state $\kappa$ and the slope change in $\kappa$ at $T_c$, observed near
1/8 doping in both YBa$_2$Cu$_3$O$_{6+x}$ and Hg cuprates, are attributed to
local lattice distortions and the suppression of the superconducting
condensate, respectively. Both phenomena are proposed to arise from small
domains of localized planar holes, presumably a manifestation of phase
separation. It is suggested that the phase behavior of $\kappa$ reflects stripe
dynamics and the 1/8 doping anomalies stripe pinning by oxygen-vacancy
clusters.
