seeker, on the other thread, a poster made a point about nn being a pet name that evolves naturally and is about a relationship between a child and a particular relative. That is fine imo. What isn't fine is for a parent to make a decision (about a name in this case) and for a GP to say 'I don't like your choice, so I'm going to do something different'.
I don't think I own my children, I reserve the right, as their parent, to have the final say in their upbringing (and the name they are called) until they are old enough to choose their own way of life.
My DS2 is a vegetarian, in a house where no one else is. He decided when he was around 6ish (I think) that eating meat was cruel and he would prefer not to. So I listened and respected his choice, because he was old enough to have an opinion. He is 11 now and has remained vegetarian. So I don't think I have a right to impose my choices on him at all times.
However, there are issues where my word goes. My parents respect me as a parent and will ask me if they are not sure about whether I would allow something. If I said no, but my mum thought it was okay and did it anyway, I'd be cross because it is about respect for the parent rather than ownership.
There are few things that bug me when my parents or IL's are with my dc. I don't mind if my mum gives my boys a haircut, for example. They are old enough to say if they want this. But I'd be mad if she cut my 3 year olds hair without asking me. I also get cross when I've told my mil to not let my DC play hide and seek in my wardrobe (DS3 has broken 2, so far) or bounce on the beds and she lets them do it anyway. I feel as the mum, I have a right to say no to theses things.
Sorry, this has turned into a bit of an essay.