I never heard of this term before either. But I do understand it. Or something similar.

For us at this point in time...well maybe not now exactly. But in the not so far past. I don't think I would exactly call it a shell alter. But it does sound similar to a couple of other familiar "states" (for lack of better terminology in our body/brain's sleep deprived vocab!)

1. Thought insertion...not in the psychotic meaning, but for the weird phenomena when you realize that you are speaking/ carrying on a conversation about a topic that you know absolutely nothing about but you're not talking out of you're arse either. As you become more conscious of the words coming out of your mouth and are struggling to understand what the heck you are talking about ..then the telltale sign from my experiences, brain fog and migraine immediately start to set it in, but the words just keep on coming. I refer to this feeling as another part is jamming an ice pick of their thoughts thru me. Also sometimes referred it it as the ventriloquist act...or simply Oww! My Brains! It's down right icky. :yuck:

2nd thing that I have come to realize is that once a part begins to accept the outwardly reality of the body's born identity. We begin to watch how outsiders act and react as well. And the next step is fuzzy in the details of how it occurs, but while we do maintain our individual sense of agency..we try to blend in a bit I guess? Like whatever a part sees as "normal behavior" from outside and whatever knowledge if any they may be aware of 1or more inside parts outward behaviour and possibly even way of speaking..I guess for most of us likely from writing style?..and others like myself from some periods of co- conciousness..
...... sorry brain really not top notch at present...

My point being is that although we remain as autonomous as possible, we get used to responding to body's birth name and form our own ideas of how to TRY to appear as "normal" as possible esp. In public. Certainly not all parts accomplish this. Some better than others. But, for me at least I'm OK with us appearing kooky or just kind of off kilter..as long as we are able to contain our "full individualness" until at least behind closed doors!

I have heard very mixed reviews from many sources... some no clue that we are any different than any one else.. (with mental issues)...all of the way down the spectrum of who the hell are you? And what is wrong with that crazy girl?
Lucky for us...most people really seem to have a hard time grasping the idea of multiples..not generally worth trying to explain outside of those trusted...because, in the past I have made this mistake and the looks! Oh Boy! I might as well be trying to tell them that we are Martians!