There are known mechanisms, but they are recorded and discussed among the mystics and esotericists. There are long, though obscure, documentation on these different phenomena. They are outside what is accepted by the mainstream consensus, so I can see why you would consider those mechanisms as being "unknown".
I probably should have explained this part better. I wrote in a different comment, but let me make this clear:
1. What I mean about "subtle energy" is not the same as the "energy" of physicists.
2. Subtle energy is experienced by some people. Not everyone is aware of how various forms of subtle energy affects people and non-living things.
3. Not all forms of subtle energy is the same
4. Subtle energy is responsive to will and intent.
5. The problem is that, what we experience as consciousness, is in turn influenced and agitated by subtle energy.
6. Subtle energy carries information: emotions, concepts, awareness, sentience. Some forms have higher "content" than others.
6. Reiki is a specific form of subtle energy, but no one actually knows where it comes from or why attunement works. Attunement is supposed to tune a consciousness to the source of reiki, but no one has luck finding out what that source is. If they have, they are not talking. My friends (I am not attuned myself) who were attuned had tried, but not luck finding out about it.
7. At best, the characteristics we found out about it is that it is universal (rather than personal), non-local, is not qi (despite the name), is not emotional, or elemental, or fluidic. It is very "light", without much substance (compared to some other forms of subtle energy). We were trying to understand this in order to distinguish it from secondary effects that _do_ have locality, or are experiences of side effects that are personal. (In other words: what are the experiences a practitioner have to know that what they are doing is working?)
As far as how it effects disease, there are a lot of literature on that. Again, not in the mainstream consensus.
It isn't just regular "energy". Some people have tried to copy subtle energy and play it back en mass. The mechanism they use is similar to that of homeopathy. How effective it is ... I have my doubts, but maybe it works. Since we (people who practices Reiki) don't actually know the Reiki source, I also have doubts we can copy it mechanistically.
> What I mean about "subtle energy" is not the same as the "energy" of physicists.
There you go. This is why the idea is extraordinary. There is the energy of physicists which explains the motions of the planets, the vibrations of crystals ;), and the mechanics of your computer. In fact, it is the theory we have for everything in the universe except the phenomenon of someone touching someone else while thinking a special kind of happy thought.
> Subtle energy carries information
Regular energy carries information too. How do you think radio works? Or how cosmic background radiation yields knowledge about what happened just after the big bang?
> The problem is that, what we experience as consciousness, is in turn influenced and agitated by subtle energy.
How? What does the subtle mechanism look like? What are the corresponding subtle equations, subtle algorithms or subtle models?
I probably should have explained this part better. I wrote in a different comment, but let me make this clear:
1. What I mean about "subtle energy" is not the same as the "energy" of physicists.
2. Subtle energy is experienced by some people. Not everyone is aware of how various forms of subtle energy affects people and non-living things.
3. Not all forms of subtle energy is the same
4. Subtle energy is responsive to will and intent.
5. The problem is that, what we experience as consciousness, is in turn influenced and agitated by subtle energy.
6. Subtle energy carries information: emotions, concepts, awareness, sentience. Some forms have higher "content" than others.
6. Reiki is a specific form of subtle energy, but no one actually knows where it comes from or why attunement works. Attunement is supposed to tune a consciousness to the source of reiki, but no one has luck finding out what that source is. If they have, they are not talking. My friends (I am not attuned myself) who were attuned had tried, but not luck finding out about it.
7. At best, the characteristics we found out about it is that it is universal (rather than personal), non-local, is not qi (despite the name), is not emotional, or elemental, or fluidic. It is very "light", without much substance (compared to some other forms of subtle energy). We were trying to understand this in order to distinguish it from secondary effects that _do_ have locality, or are experiences of side effects that are personal. (In other words: what are the experiences a practitioner have to know that what they are doing is working?)
As far as how it effects disease, there are a lot of literature on that. Again, not in the mainstream consensus.
It isn't just regular "energy". Some people have tried to copy subtle energy and play it back en mass. The mechanism they use is similar to that of homeopathy. How effective it is ... I have my doubts, but maybe it works. Since we (people who practices Reiki) don't actually know the Reiki source, I also have doubts we can copy it mechanistically.