I have many "plain text" notes that were created in the Windows Evernote client which are editable via the mobile client (which does not allow editing "rich text" notes). Editing these in NixNote converts these to "rich text". The way to get around this would seem to be create a new note, copy and "paste without formatting" the contents of the "rich text" note into a new note. But when you do this and save the note, the new note is also a "rich text" note.
If I cut and paste the text into gedit and then into a new note, this function is also broken.
if you take the following text and type it in gedit/leafpad/vi whatever, and then create a new note and "paste without formatting" it into the note, when you save you will have a "rich text" note.