it gives me creepy crawlies when people talk of communicating with my soul for purposes behind my back, regardless of the intention.
But is it really any better than sending something you may not want behind your back?
Communicating with your soul is communicating with YOU, not a part of you, so it's not behind your back.
To each his own, but I am used to arguing some of what is true and what is not on Reiki boards, so excuse me because I normally would just post, "You belive yours, I believe mine," but you have triggered the debate-hungry side of me.

I must draw on personal experience, as well, because so much in Reiki is under debate by various people who don't want to be traditional, who do want to be traditional, who want to just disturb some s***.
So, I will have to disagree secondly that one has perfect ability to accept or reject whatever you send at them. After all, look at spells. Matter is energy (all things are energy in some form or fashion), and I don't believe we can choose to reject or receive everything any more than we can choose to reject or receive a hard punch to the gut, no matter what the intention (say if you are choking and it ends up just cracking a rib). We of course are often able to block it, but many time we can't. How many spells can you really prevent or block against yourself? Sure we all have the ability, but in practice how many can and do we block?
The notion of having permission first a) shows respect for the being and b) prevents any karmic backlash in case you are wrong. Asking them in person is the same as asking them on the astral plane.
From personal experience I have noticed an incredible difference in some individuals when I asked them on the astral plane. Early when I had my Reiki II, I had forgotten to ask for permission on the astral plane. I felt badly when I realized this, ended it, and them asked that it go only with their permission. The amount that was channelled through was incredibly different. This has only happened twice, as now I make sure to ask permission
every time and not forget.
I don't know quite what to say to your comments about asking the soul being arrogant. How else are you to find permission if the person is in a coma, or it is an animal? When you ask the animal in person, waiting to receive the answer, what is it that communicates the answer to you? The astral body, or the soul.
I don't see the soul the way Xians do. The soul is the free body, the part of you that is free of bonds and travels around and goes Out Of Body. It is not something separate. It is your essence. It is you. The rest of you is just a shell, a means to communicate to another shell your permission or not. Asking the soul is just asking without having to enlist the aide of the physical body.
Okay. I am tired now.

If you find any mean tones in my post I assure you they are not intentional.