“Dad” in the first example is a description, not a name. It’s a common noun, not a proper one for the simple reason that it implies that there is more than one dad – you say “my dad” in order to specify that it’s not Joe’s dad.
“He’s my dad, I call him ‘Dad’” is capitalized correctly. It is however a comma splice and should be either “He’s my dad. I call him ‘Dad.’” or “He’s my dad; I call him ‘Dad.’”
It’s the same thing with the other terms of endearment. They are common nouns, not proper ones.
RealityChuck & Maserschmidt, thanks very much, especially for the explanation.
It’s only one member of the group who’s brought this up. I wouldn’t have worried about it except I was already fretting on the common/proper noun thing. Noted the splice comment.
TB, gee, thanks for playing. May Gaudere haunt your keyboard as she haunts mine.