I see what you are getting at, not from the host point of view but from the alters points of view how did they tell who was things, who was talking, who was debating.....

short version each of my alters had their own way of being, their own jobs, purposes, reasons for being created therefore their own identity, their own perception of who /what they were/...

example
Sunny (not the alters real name just throwing names in here for example purposes) was my alter that was outgoing, happy, energetic, ..how she presented herself in the world and with in the system was like this.

Rainy was my alter that was depressed, withdrawn, .....everything that made up who/what she was and how she perceived herself was total despair.

Trixie was my sexual alter....everything she was and how she perceived herself was make up fancy dresses and ...well sex.

so how did these three alters know who was talking, who was debating, who was arguing.....

Sunny....(in a cheerful, happy energetic voice)...Its nice out I want to go for a walk

Rainy...(.in a weepy voice) no I hate being outside, its horrible, anything can happen

Trixie....(in her sexual voice)))) oh yea lets go find us some huh....

with DID each alter has their own special identity (their own way of being, their own job, purpose, reason for being created and perceive their self)

they all just know they are who they are and the others are the others and how to tell each other apart.

thats not saying some with in the system may not know everyone with in the system. how much and what each other knows about each other depends on what each one shares with each other....

example...

my alter martha (again just throwing names together for example purposes) didnt share what and who she was with Trixie because that was not part of who/what martha was, it wasnt in martha's job, purpose, reason for being created nor was it part of how martha presented and perceived herself and her environment... to Martha she was an only child, a solo identity that did not need others to survive, she relied on her wits, and self educating ways.

because it wasnt with in martha to share, co operate with others, need others those with in the system.... the others in the system did not know the strange voices, words, ....was Martha.

they never knew anything about martha and martha them because there was no sharing, no co consciousness developed between them. it just wasnt with in martha to do that.....

my suggestion is if this continues to bother you, contact your treatment providers, they can help you learn who is who and who does what with in your system and how to tell each other apart if its with in you to learn this information from your system.