Excellent project, congrats! About the cleaning up phase: the author cleaned up the bitmaps before the vectorizing stage, and that included separating lines.

Excellent project, congrats! About the cleaning up phase: the author cleaned up the bitmaps before the vectorizing stage, and that included separating lines. In my experience it's a little bit easier to clean the vectorized results by removing unwanted points, because those are easier to see than line connections that may or may not pose a problem later. (But to each their own.)