If exchange is an interaction between indistinguishable particles, how can there be an exchange interaction between electrons and holes? I see mention of e-h exchange often in the literature.
Hole is not a particle. Microscopically, hole is a quasiparticle perturbation of many-electron system. And what is called electron in semiconductors is also a perturbation in the same many-electron system. Exchange interaction within this many-electron system results in a complicated interaction between quasiparticles which live there. Which is called exchange interaction because it is quite similar to "normal" exchange interaction.