Academics are probably afraid to talk about it because they don't want to believe that they have other people living inside their brain.

Religious/spiritual people don't want to lose their religion. They want to believe God speaks to them, not a god alter that they and peers created.

I for one want to talk about it because it's real and it's happening. These inner people exist. I have experience seeing normal people create them and start hearing voices from people who have real personalities.

I don't want to call them spirits. Alters is best name. For ages people in spirit community, more like the new age type of movements, know full well that nearly everyone can be taught to hear spirits if they put enough time and effort learning it. I'm certain that most of them are alters, not spirits. Try asking a good medium to have a spirit tell them what number a random role of the dice are inside a box? Good luck. I've tried plenty of times. These "spirits" can't do it without the occasional luck. So looks like they're alters.