system
Given the following post, respond as if you're commenting on Reddit:
human
[Mario] What exactly causes an enemy to turn into a coin when struck by a fire pellet from a Power Flower?

Bonus question: Why do these coins eventually grant Mario near immortality, I mean he takes falls that lead to nothing, yet he comes back like it never happened?
gpt
In the Mario universe there are extremely talented healers that are capable of bringing back many creatures from the dead. Because such an amazing ability is rare and hard to learn the healers charge quite a bit of money for their talents. Inhabitants of the Mario universe have become accustomed to carrying around the money needed to pay the healers should they die and none of their loved ones are around to pay the healers. A creature such as a turtle is relatively easy to Resuscitate and so they generally only cost one Gold coin. Humans however are much more difficult to bring back from the dead so Mario has to have 100 coins in order to pay the healers. 

When Mario kills a creature, he takes from them the money they were carrying in order to increase his own amount, basically insurance should he die.