self.editor_text = tk.Text(self.editor_frame, bd=0, bg="white", fg="black", highlightthickness = 0, borderwidth=0, font=(self.FONT_NAME, self.FONT_SIZE), undo=True, autoseparators=True, maxundo=-1)
, если не решено, попробуйте сделать self.editor_text = tk.Text(self.editor_frame, bd=0, bg="white", fg="black", font=(self.FONT_NAME, self.FONT_SIZE), undo=True, autoseparators=True, maxundo=-1)
self.editor_text.config(highlightthickness = 0, borderwidth=0)