That's the point I was trying to make in that other post: the First Law of Thermodynamics says energy cannot be created or destroyed, only transformed from one form to another. A conventional lightbulb, for example, converts only 10 % of the electricity it consumes into light, the rest is dissipated to the environment as waste heat. This means that not all energy is realistically recoverable or can be converted back into its original form. If we take the electrical energy analogy for subtle energy too literally, similar limitations analogous to the First Law of Thermodynamics would apply, which would clearly be unsatisfactory. For example, it would prohibit the phenomenon that subtle energy can be created from thin air, or that it can simply vanish without a trace. Which is why I think that magic shouldn't lean on physics too hard for analogies and consider alternative ones like the information model as well.
Imagening the soul to be 'pure energy' while willy-nilly thinking of physical energy with all its bothersome limitation is difficult. Considering it an information-dense unit is easier, maybe encapsulated in karma which could be thought of as yet another information package deciding its subsequent fate. Physics analogies have its downsides, is what I'm saying.