[nxobject]

I'm always saddened by the distinction between "user level C++" and "library level C++", but I hope it's gotten better over time. I remember once trying to write my own shared_ptr clone after the release of C++11, and having to learn as I went about why reference collapsing was invented was very, very discouraging.

[zabzonk]

i think the distinction exists in most languages - in the case of libraries you are trying to make things easy for callers of your code who's motivations you cannot understand; in the case of application code, you probably do have a pretty good idea of how/why people might call it or try to extend/maintain it.