There has been a lot of controversy over the last few years as to whether Reiki healing symbols should be secret, sacred or neither.
At one time, all the symbols were kept secret to the extent that the Master/teacher told the students to memorise them and destroy any written images of them.
My teacher/master do not feel that they should be secret. It makes no more sense for her to hide the symbols than it would to hide a cross, or a Hold Grail (if already found) or an APPLE logo.
A symbol *stands for* something. It is not the 'something' itself. Even if it was, universal life force energy is already everywhere... how do you hide that???
As for sacred, according to my teacher/master (Note: She heard it from another person but could not remember whom though):
"I believe in nothing, everything is sacred; I believe in everything, nothing is sacred." Sacred is, I believe, in the eyes of the beholder. And for me, I love to share and glorify sacred things by showing them."
My master/teacher only share the versions of the symbols given to her by teachers who share his/her views. She also organises regular workshops for her students(Note: Unfortunately, she is based in India). In her workshop, she shares many, many other methods and symbols with her students. How I wish I could beam myself to be in her workshop in a blink! Sigh!
According to my master/teacher, ultimately, healing is always up to the energy and the client, regardless of the practitioner's actions or lack thereof. The intent is important. If any Reiki symbols is used for bad intent then it will NOT work. Reiki is all about good intent.
Reiki can only be given with a positive intent. No one wants the bad Karma. It helps to release the negative energy trapped by the body on the physical, mental, emotional and spiritual level.
Note: I have nothing against those masters/teachers who teaches students to keep learning method and symbols a secret. However, I sincerely feel these teachers are 'old-school' and very typical old-fashioned. They probably live in so much fear that their mind is so closed to be open. Only when you go to them, then you get the knowledge (maybe some and not all). That is why lots of valuable knowledge from the East dies with its master/teacher. Nothing in written format. Sigh!