Where do you draw the line on "smart" features? Tab should not add indent spaces? Encoding or newline mechanisms? Determining EOF newline?
For a very basic default editor, I would expect it to include only what I typed, no "smart" features, no IDE features, nothing else, and use CRLF (on Windows) for newlines with at most a setting to configure it in the editor for that session.
Basically, I wouldn't expect anything more than what nano does. If I want a fancy CLI editor, I'll install one. At its core though, it should exist only to edit the text content of a text file and do nothing else. It should be as stable as possible, and have as little scope as possible, in my opinion.
With that said, basic text editing features, like undo/redo and cut/copy/paste would be nice. Bonus points if it even works with the system clipboard.
Edit: to add to the question of whether an automatic newline should be added, Windows has no requirement for terminating text documents with newlines, so I would not expect one. What happens in POSIX environments by tools written for those environments seems irrelevant here - if a valid text document in POSIX must be terminated by a newline, then a text editor there would naturally be expected to add one, or at least support adding one, but that has nothing to do with Windows.