For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Was it Jesus then that spoke with Abraham in Gen 18:1 NKJV - Then the LORD appeared to him by the terebinth trees of Mamre, as he was sitting in the tent door in the heat of the day.
They spoke and the Lord and the ones with him ate. Sarah also heard him, but she was in the tent and I'm not sure if she saw him??
Abraham also walked with them while he plead for Sodom.
As believers we agree Jesus is God while he was wearing flesh. Physical people of his days, actually saw God in a different form (fleshy form) and not in his original heavenly form. That may still apply to Moses. Moses may have seen God "face to face" in a different form, other than his original heavenly form. So in essence, no person can see God in his original form and live, but we can see God in another different form and live.