Can Creator share with us why this kind of dramatic sharing of a body by two separate souls is so rare—or is it? Could it be that it’s more common than we think, but not recognized for what it truly is, and the signs overlooked or ignored?

This, indeed, is more common than one would think. Because it is little recognized by psychologists or physicians, any hints of such phenomena as spirit possession are assumed to be either a temporary aberration of fantasy or a dissociative state of temporary imbalance, where a person is not quite themselves but in an altered state of consciousness that might be subsumed later. So the person will not be acting like themselves in the moment, but is that considered as evidence they turned into someone else or that someone else has suddenly shown up within their physical form to take over? The host will often not appreciate what is going on either. Many, many people have a voice in their head they do not understand and many fear they might, indeed, be mentally ill, which is usually a diagnosis given in such cases, that someone is suffering from psychosis, a delusional disorder of some sort that makes them uncertain who they are for a time, and to take on another persona as a defense mechanism to help them cope, perhaps with intolerable inner confusion and stress, and so on. Most people have spirits within them that can be induced using hypnosis to talk with the subconscious mind to step forward and speak through their host. That is a garden variety phenomenon that can be demonstrated by any competent hypnotist with suitable training. The ease with which this can be done, and the frequency in which it can be demonstrated successfully, speaks to the commonness of spirit possession as a phenomenon. Fully 90% of people have dark spirit meddler attachments and there are many with a lost soul human spirit as well, or a hybrid of the two types, inhabiting a person who will most commonly be completely unaware there is another consciousness, or multiple sources of consciousness, within their energy. But there will be consequences nonetheless because most of the interaction and conversations and manipulations from the interloping consciousness will take place in the deep recesses of the mind, what you have discovered and call the "deep subconscious," and this can be quite disturbing and have long-term repercussions for happiness and well-being as a constant potential threat.