The following is my answer to the question:
Full time true self (enlightened person) never asks such a question because s/he knows s/he is the whole cosmos. So, "Who am I?"'s "I" is ego or temporary true self (those who are mindful temporarily but aren't enlightened yet). Ego or temporary true self is asking "Who am I?". The answer to "Who is listening?" has three patterns. If ego is asking "Who am I?", only ego is listening or ego and temporary true self are listening. If temporary true self is asking "Who am I?", ego and temporary true self are listening.
When I had two versions of myself, I asked to myself, “How can I stop rejecting myself? How can I love myself?”. And I found out that "I" was ego and "myself" was temporary true self as follows:
How can I (ego) stop rejecting myself (true self)?
How can I (ego) love myself (true self)?
* True self of above means temporary true self (those who are
mindful temporarily but aren't enlightened yet).
So I needed to transcend duality.
Therefore, there are three versions of oneself which are ego, temporary true self and full time true self. Evolution of humanity means the evolution from ego to temporary true self, and the evolution from temporary true self to full time true self.
(Reference 1) http://www.slideshare.net/compassion5151/3-versions-of-oneself
(Reference 2) http://plumvillage.org/news/unconditional-acceptance/
(Good news on Thay’s Health) http://plumvillage.org/?p=7391
Bliss Photo by Jackie Lewis