Wang Qi still remembers, when he attended an elective course at Xinyue Immortal Institute, the main content included more than ten laws about "transcend tribulation", common methods, etc. Because the content of that class was somewhat interesting, he listened quite attentively.
That class specifically discussed the ethical issues one needs to face when replacing a physical body and transcending tribulation.
Possession is an absolute illegal act, and once discovered, it's the death penalty without negotiation, so it won't be discussed. Generally speaking, reincarnation is the least recommended. Putting aside how many cells are still active and how much protein has hydrolyzed in a corpse after death, just dealing with the social relationships of that corpse is an utterly troublesome matter.
