I do this as well, so you are definitely not alone! I tend to have long conversations with people who aren't there (Things I wish I had said during an earlier discussion, things I would like to say in a future discussion...etc.). I am able to speak confidently to these people when they aren't there and speak so clearly which is a big difference from my fast paced, jumbled talking when I'm face to face. I also tend to talk to myself in third person a lot and narrate my life verbally and in my head.