Oh, I have no problem with the flake label, rather suits me!
But - as I said, I do not lie and I do not delude myself and others, and would never dream of offering anything to anyone (let alone charging for it, which I do sometimes) if I did not know 100% that it is beneficial. I often treat a friend for a bad back and her husband couldn't understand why it makes her feel better so he asked my dh if I was hypnotising her
.
My daughter has a mystery rash right now. Reiki helps her to feel better but here I'll put my hands up and say she also needs something more to stop the itching. She's got Eurax lotion, which contains an anti pruritic but 'it is not yet known how this works'. Which is fine, I don't need to know how it works, I just need to know that it does. Reiki is the same. One day I really do think we'll understand how it works in the same way that we understand radio waves, x-rays and of course electicity and the like.
You can add mystical elements to Reiki, but no more than you do to massage or yoga. Unfortunately when Reiki came to the West the lady who brought it ended up in the States just after Pearl Harbor. It wasn't good to be Japanese just then so she added in lots of cod religious stuff about Mikao Usui (who founded Reiki) being a Christian mystic and going up a mountain for forty days and whatnot. He wasn't; he was a Tendai Buddhist and Reiki comes out of the same school of thought as martial arts such as Tai Chi.
I have tried many different 'alternative' routes down the years, with no real success, and I wasn't expecting anything of Reiki either. I only went for it on a mnetter's recommendation as she used it on her dc who had SN.
I couldn't feel anything; I was attuned to Reiki, then I could. Primarily my hands get hot; I feel my hands get pushed away, or there is a coldness, or nothing. Very rarely I get knocked off my feet. When I receive Reiki I see lights and feel like I've just had several scotches. 
I often give people treatments who are very sceptical (I don't charge in this circumstance) and who are stunned by what it does for them, but sometimes I do get someone who wants to 'prove' that I'm a fake and in that case I feel the energy block. Because Reiki is ultimately about taking the energy and healing yourself, if you don't want it then you won't feel it. I know that sounds like a cop-out but that's how it is, because any Reiki practitioner is just a channel and it is up to the recipient to accept the energy.
And anyone can be attuned to Reiki, it's not a gift you are born with. I'm not a healer.
As for attuning dd1, it's only a step up from a treatment. I just ask that she recieves the energy herself. Some Reiki lineages make it very complicated with lots of symbols but I studied through a group that have learned in Japan and it's very simple when taken back to its roots.
What does concern me is that we're in danger of banning anything that can't be 'proved'. Just because we can't understand something, that doesn't make it fake.
I will try and find the reference to the diabetic study but it's in my beginners manual and I don't know if I still have it.