I think we, for cultural purposes, need to get away from the "d" and "D" distinctions. It's just that the medical model is standing in the way of this....if that could somehow be shoved aside, then from within the cultural model, the two distinctions should be torn asunder.
You have a couple of excellent points, Tousi. The first is in English there is no special distinction that comes from arbitrary capitalization of a common noun, except that careful and knowledeable readers know it's a bogus attempt to convince others of inflated importance. We tend to do that with all kinds of words. Some of it comes from the language’s Germanic roots. In German,
all nouns are capitalized.
I think fear of God started it. "I begged God to help me" is correct; it's used as a name. However, "I begged my God to help me" is incorrect, because in this case, the speaker is not using a name of a specific deity, only the general term for one of several deities. It's not blasphemy; it's just that in the context, god is a common noun.
Not to be outdone, royalty wanted king and queen capitalized next, even when it was “The queen visited The House of Lords today.” “Queen” is a common noun, but House of Lords is a proper place.
Then of course we in the Americas want our positions of prime minister and president to be capitalized at all time. Sorry, it’s just as wrong as the king's English.
We Catholics are guilty of spreading the false idea that capitalization somehow means respect. We see Father, Sister, and Brother as part of clerical titles, so we capitalize them all the time and extend it to mother, mom, dad, etc.
In addition to teaching duties, I was the education director at a campus hospital. Naturally, the physicians think they’re god-like, so they wanted “doctor” capitalized. I spent a lot of time editing them down to size. But then nurses thought they were every bit as important as doctors, so they wanted their profession elevated to proper noun. Next the physical therapists figured they make as much money as nurses (and some doctors) so they want in on the grand pretense. It goes on and on within the medical profession until it’s ridiculous.
Naturally, we teachers want our profession to begin with a capital--actually, I think it should be TEACHER in all caps.
The difference between "I am deaf" and "I am Deaf" is really nothing but confusing pretense.