This issue is probably because the text is not being rendered smoothly. Smooth rendering is required when high res images are shown on low res screens. Text is generally very high res. That's why it is only appearing fine in retina display. Still, it's not smooth even on a retina display and retina display users can tell the diff in main right side screen against text in the new window using a magnifying glass. The note text in a new window or in web browser looks great because it's gone through smooth rendering. Problem is just on the right side display inside the mac app.
I can see from