Your comments

The 'text font' setting at position 1 applies correctly in the note list(position 2) but not in the editor(position 3). Is it a bug?
Yes, these are steps to represent the problem:
1. change note editor font to a non-monospaced font--for example, 'Microsoft Yahei'(微软雅黑);
2. create a new note, add some text then close it;
3. reopen the note, you can see the font of the previously saved text is not the specified non-monospaced font;
4. type some new text, you can see the font of the new text is the specified font.

I think it has nothing to do with the character encodings. The same problem occurs  when just using ascii characters.