"Living with an invisible disability, as I do, my three DSs do and my Dw do, does not mean that our disabilities do not exist, as you have suggested."
Could you point to the part of my contribution to this thread, where I have suggested that your disability does not exist? I haven't, not once. In fact, I am saying the complete opposite. I am saying that the moment your APD manifests itself in a day-to-day situation, it stops being 'invisible' and becomes 'visible'. The only issue then is whether the onlooker 'sees' the manifestation of APD, or sees ignorant behaviour, or sees rudeness, or whatever conclusion they may jump to.
I am saying that as parents, we have the choice to either get cross because they jump to the conclusion that matches their experience (ie. the child is being like 99% of other children = naughty behaviour) or we provide them with one step on the path out of ignorance, by simply saying 'oh x isn't being rude, he has APD, so he didn't process what you said....' or 'oh, sorry DD1 touched you there, she has SN and is really very tactile', etc.
I am saying 'as parents' because this board is about having children with SN. I also don't think you can say "being a child with an invisible disability is nothing compared to being an adult living with an invisible disability." It is nothing compared for you perhaps, but there are many adults who have disabilities who find it much easier to cope with their disability because as an adult they have the power and resources to develop coping strategies.
An example, I would say, is Amberlight. She is an amazing woman, who openly says she struggled in childhood, but now has a team around her that enables her to reach her potential and overcome the barriers that her disability tried to construct.
I referred to ASD because the majority (almost a vast majority) have experience of ASD on this board. My own daughter doesn't have ASD as a dx. She has 'squiffy brain', but even after 3 years of knowing my daughter has 'squiffy brain', it won't fit neatly in a box. ASD is, at least on here, a tangible dx.