Q. The sixth chapter of the Bhagavad Gita says that one who has conquered his mind has reached the Supersoul. This chapter is told in the context of laying out dhyana yoga. But, we practice bhakti-yoga. Does a pure and realized devotee of Krishna (here, I mean the devotee has conquered the mind, too) see Krishna in everyone's heart or the Supersoul? If the answer is "Krishna," does he in any circumstances see the Supersoul?
Realization of the "Bhagavan" feature includes realization of 'Brahman' and 'Paramatma' features. It is the most complete picture of the Absolute Truth. A pure devotee sees the Supersoul as Krishna. He sees the Lord in His Shyamasundara feature - in everyone's heart. This is confirmed in Brahma-samhita:
santah sadaiva hridayeshu vilokayanti
yam shyamasundaram acintya-guna-svarupam
When we speak of differences in realization of the Absolute Truth, it is in terms of realizing the different features or characteristics of the *same* Subject. When a brahman-realized person interacts with others, he sees them as an energy of the Supreme. The vision of paramatma-realized yogi is more evolved -- he sees everything and everyone in relationship with the Supersoul -- which is but a clearer vision of brahman. Whereas a devotee sees everyone as servants of Krishna, and Krishna reciprocating from within the heart. (Recall the example of the Sun, or a hill, studied from afar, and then closer, and further by entering into the Sun or the hill itself, and clearly seeing the personalities there -- the subject is the same in each case, the difference is in one's vision.)
We see according to our vision -- the same object carries different meaning to different people according to their vision -- a loving mother sees a lot more in her child's shoes than a stranger would.
The paramatma-realized yogi can appreciate some features of the Lord -- His feature as Supersoul -- such as His being the source of everything, His superintendence over material nature, His being equal to all living entities, giving them remembrance, forgetfulness and knowledge etc, but such a yogi does not have realization of the more intimate features such as the sweetness of Krishna's nature or His loving reciprocation of Krishna with His devotees. But because a devotee's eyes are anointed with pure bhakti, He sees the Original Supreme Lord, Govinda or Krishna, even while perceiving the activities of the Supersoul such as His maintaining the material creation, or His being a witness to our activities.
This idea is more clearly illustrated in the description of Krishna entering the arena of Kamsa, where different persons saw Him differently at the very same moment - the wrestlers saw Krishna as a lightning bolt, the yogis saw Him as Supreme Truth, the unintelligent saw Him as universal form, Kamsa saw Him as Death personified, while His parents saw Him as their own darling son. (SB 10.43.17)