Thanks for clearing that up. And yes, I was playing Ermor and fighting against Tien-Chi. I didn't know how that Death 9 blessing worked, and I had a whole lot of those sacred undead knight in that battle that killed him.
Hmm, couldn't find any references to "reincarnation glitch" using the search function.
In case anyone is interested in the specific circumstances (for bug-fixing or to reproduce this effect):
I was holding the Tien-Chi capitol fort. Li T'ieh Kuai led a bunch of troops to take the province. I ordered my troops to break siege and he died in that battle. The next turn, he was reincarnated in my capital.
The fact that you were holding Tien Chi's capital, where Li T'ieh-Kuai normally would have respawned, could be significant. Or it could be a coincidence.
The glitch can only affect immortals that don't get resurrected through normal immortality, so holding the tien chi capital could very well have been significant, unless the battle also occurred outside of tien chi dominion.