[dgb23]

> I've never once in 10 years had an issue with a public field that should have been private, however I have had to hack/reimplement entire data structures because some library author thought that no user should touch some private field.

Very similar experience here. Also just recently I really _had_ to use and extend the "internal" part of a legacy library. So potentially days or more than a week of work turned into a couple of hours.