Seer,
I will try to answer your question from what I know of my lineage. II Levels and Masters were asked to pick a dominate hand to use to draw symbols and pass attunements. This has evolved to where I belive most Masters attune both hands.I am not sure about the receive part since we are passing the energy not receiving it. The Master that I studied under was originally attuned in one hand, her non-dominate hand. She has sinced been attuned in both hands and attunes her students that way as well.
I cannot speak for what you term contmporary Reiki. I am a Reiki Master who practices Usui Shiki Ryoho. I have a very traditional outlook towards Reiki and have been known to be called a purist :-)
Please don't feel like a fish out of water. Reiki is a wonderfu blessing.
Blesings!
Reikilady
