context of comparisons
Don't get lost in the research of a particular sect finding the use of sound, such as Kotodama sounds.
It is a fascinating study, but so too would be the use of sounds in religious music, chanting for religious ceremonys, or the use of sounds for healing or even martial arts.
The complications of studys is sometimes the mask for the simplicity of their use ... it works best this way, so we do it, this way.
If you take the time to compare the sounds of your life, the sounds that make you feel better, or sounds of nature, you will find that the many root sounds do have simular effects across the board to every corner of the world ... even if they have slight variation.
We are part of the ecology of Mother Earth, even if we don't always consider ourselves so. Just as much as the sounds of the wind, the water, the creatures of the earth take meaning with each culture, there is a simularity of sounds that are interpreted with the words and combination of sounds to cause effect, or change.
So, although the Kotodama is one expression of these sounds, I wouldn't throw myself into expressing a life's commitment to this very Japanese pursuit. I think it helps to understand the cultural context of Aikido, but as many things in life, it is not for everyone.
As far as pointing to those who have used it, or tried to use it to understand O'Sensei ... that too might be a matter of knowledge, partial insanity to understand the thinking mind, and many years of experience to have some of the same stimuli to effect those same thoughts.
Get out there, experience some of the Kotodama, and make your own opinions on what it does or does not do.