For what does it actually mean to be supra-personal? It's a word the meaning of which no one can really understand. To begin with, how does it differ from impersonal? It strikes me as potentially a gambit used by non-dualists to deny the reality of the personal or demote it to a lesser and relative state. It can certainly be employed to that effect. Therefore those who advocate the idea of reality as supra-personal must be careful to differentiate between that and the impersonal, and make sure they are not re-introducing the latter through the back door and under another name. If supra-personal is compared to personal as a sphere is to a circle that makes theoretical sense because at least then it can be conceived of as something including but more than a person (rather than less than one as impersonal undoubtedly is). But even so this is still just a theoretical concept, and the idea that God is a Person, not supra-personal or transpersonal (vague terms that carry very little meaning and which can be used to deny real personhood to God) is the only real basis on which it can be said that God is Love. A personal God is still the only way in which we can have a relationship with God which, according to the Christian idea, is the goal of the spiritual life. And it is the only way in which values of goodness, truth and beauty can have any real meaning. That is to say, meaning fundamentally rooted in reality. For only if the person is real can anything be real, other than pure undivided consciousness. And maybe not even that.
So, all things considered, I don't think that conceiving of God as supra-personal is all that helpful. While it might help to describe an experience of the ground of being it should not be used to support the reductive view of the world that advocates of non-duality incline towards. God, no doubt, cannot be limited to a person as he cannot be limited in any way, but if we truly are made in his image then this must be an important and real part of what he is.