I'm not sure I really understand what you are asking here.
Are you asking about commonalities between people with auto-immune diabetes diagnosed when they were children? Because yes, I would agree with you that people who went through this have a shared experience of something terrible and traumatic.
Or were you referring to 'adult-onset insulin-dependent people with diabetes'? Because this is not just classic Type 1 people.
I recently attended an insulin-dosing workshop where we were taught to adjust our insulin to our food and our lifestyles. For me the best part of the experience was meeting other insulin-dependent people in person and sharing experiences and tips - stuff that the nurses would never tell you, like how it's ok to reuse your lancet lol.
Of the 10 people there, only one had been diagnosed as a child. It was interesting and often heart-wrenching to hear her experiences of being diagnosed aged seven. But all the rest of us had been diagnosed as adults (21 and older) and had had the chance to live 'normal' lives so as much as we could empathize, we could never know what it was like to go through that sort of childhood. So obviously, the adult-onset people had a different set of experiences and issues compared to what the juvenile-onset person had gone through.
Of the 9 adult-onset cases, 8 had antibodies, one did not. Me. But I live my life the exact same way as they do - except with less carb in my diet and more insulin resistance!
Your post unnecessarily polarizes PWDs into artificial 'categories' which don't capture the fullness of shared experiences. For example, the shared experiences of those who were diagnosed with insulin-dependent diabetes as children, which are quite different from the shared experiences of those diagnosed with insulin-dependent diabetes as adults. 'Type' doesn't come into it. Do you feel you would have nothing in common with someone who was insulin-dependent, who had got there without an autoimmune episode? Or do you need the presence of antibodies to feel a connection?