I don't have an autonomous internal monologue, but I can speak in my mind, meaning just like actual speech but without the physical sound making. But it's not some other entity saying stuff.to be honest, if someone told me they hear voices in their head I would assume they are not 100% alright mentally, which is totally okay of course but I'd suspect perhaps they should seek treatment. Now that I'm seeing so many commenters (probably a biased self selected sample though) saying they hallucinate all the time,see entities and hear voices, I'm less sure and perhaps it's normal?