great question

After reading this post yesterday I checked this out with mental health treatment providers here in NY which is in the USA. the unanimous answer is no. once co consciousness is established it can not be reversed/go away/lose it...

that said a person with dissociative issues or not has the ability to ...ignore/not pay attention to/convince their self its not there just like if someone (a friend, co worker, therapist, family...) tells a person something they dont want to hear they can ....choose not to hear it (its called selective hearing when this happens) Just like normal people can be very selective on what they hear/accept and want in their lives a DID person can also be ....selective....on what they want to hear and accept from their alters.

my therapist used the example of a time when I heard an alter say they had to do something I the host understood to be wrong..I heard it but for me it was like the phrase in one ear and out the other ...it came in to my head and my logical mind disregarded it and pushed it back out just as fast. At a later time I took the offensive...you didnt tell me about that attitude because to me I didnt hear it, but a bit later I realized crap they did tell me that..

another therapist in the area used the example of a parent telling a child to go do their homework and then the child can watch some tv. the child focuses on the words ....can watch tv instead of what they dont want to do...their homework. the child goes to watch tv and gets in trouble because their homework isnt done and the child says....you didnt tell me to do my homework first....A DID person has the same ability to focus on only what they want to hear like the child who wants to watch tv and not do their homework.

a person being selective in what they will hear /accept from their alters is different then having co consciousness.

co consciousness is things like...

hearing voices
knowing your alters exist
knowing what those alters do
knowing for example Red likes black clothes and Sunny likes bright vibrant clothes
knowing some of the alters memories
some people can feel what their alters are feeling
finding an alter has bought something you dont remember buying
finding art work done by the alters (if the alters didnt want to share this with a person they would hide it).......

theres all different dimensions to being co consciousness.

theres no way to go back to not knowing after an alter has shared their feelings/memories/artwork/ that they exist, but you can be willfully selective like the child who wants to watch tv not do their homework.

selective engagement goes the other way too... alters can be very selective on what they will selectively hear/see/ understand from the host and can at times even though the host and alter is co conscious be selective on what they will share when.