Better/complete documentation of sys.stdin/stdout/stderr default behavior

See https://docs.python.org/3/library/sys.html?highlight=stdin#sys.stdin
The default behavior of sys.stdin/stdout/stderr is not fully documented (e.g. the default newline mode, depending on OS), and the current existing documentation is a lot more difficult to understand than it would need to be, referring to internal c-api settings instead of explaining in clear language what is going.

Given how important this information is and given that the behavior of sys.stdin/out/err is surprisingly DIFFERENT from what the default would be if open with default settings would be used, making the documentation more complete and easier to understand would be rather important. The number of questions on stackoverlow (partly with incorrect or hard to verify answers) about this is a good indicator of how confusing and important this matter is.

リンク先の Python ドキュメントページにある sys.stdin、sys.stdout、sys.stderr のセクションから始め、その説明を、各オペレーティングシステムでデフォルト設定を使って open を実行した場合の動作と比較します。デフォルトの改行動作とその他の関連する違いが、内部 C API の用語に頼らず、明確かつ正確に説明されていれば作業は完了です。