I have sometimes this. I spend a lot of my time alone and when I talk by myself, sometimes voices talk back to me. Example in Finnish is ‘puhuin yksin kuinka asuin yli kaksi vuotta autossa ja eräs toinen henkilö ei ole asunut’, and then a voice responded in Finnish ‘ei ikinä’. Sometimes this happens, but not very often. My voices are most often in Finnish.
No, usually I have the opposite, thoughts that I think they are external, but I think them first and then I just “answer”, by thinking something myself as an answer to these thoughts.
There are times when I get into an argument with the voices in my head… I’m not trying to be glib… but there have been times when I guess they just need the last word.
I do still mumble to myself. But for the most part… my voices have been fading. It’s sort of hard getting used to.
Perhaps I was wrong when mentioned that the “external” thoughts I have don’t “talk” back to me when I am talking to myself, that also happens to me, but I just didn’t remember it previously.