In the tag-renaming dialog, ESC is CANCEL, while in the note-editing dialog, ESC is OK.

I understand your request. Still i disagree. ESC in the note editor is a neat feature for "auto-saving" changes. For beginners this can be irritating though. Maybe a "save changes yes/no?" dialog could be added. That dialog should have an option "[ ] always save note when ESC is pressed - don't ask again".

Originally ESC canceled the edit.
Users complained that they lost their edits when ESC was pressed inadvertently.
This is why I made ESC to save the changes.
But I would hate to introduce another message box. What about making it part of the Undo function, e.g. "undo cancel editing"?

ESC to save is unusual but convenient. Except when I accidentally delete something and ESC to cancel immediately, just as i do in any other editing dialog.
In any case, undo function is absolutely necessary.

There's also a request to add autosave functionality to the editor, which is related:
http://roadmap.cintanotes.com/topic/8698-autosave-currently-edited-note/