  We study the stability of Kitaev quasiparticles in the presence of a
perturbing Heisenberg interaction as a Fock space localization phenomenon. We
identify parameter regimes where Kitaev states are localized, fractal or
delocalized in the Fock space of exact eigenstates, with the first two implying
quasiparticle stability. Finite temperature calculations show that a vison gap,
and a nonzero plaquette Wilson loop at low temperatures, both characteristic of
the deconfined Kitaev spin liquid phase, persist far into the neighboring phase
that has a concomitant stripy spin-density wave (SDW) order. The key
experimental implication for Kitaev materials is that below a characteristic
energy scale, unrelated to the SDW ordering, Kitaev quasiparticles are stable.
