There is also something I think I need to repeat, because it got buried in the discussion and probably forgotten, but it is my answer to "I can't believe that the Scribe would not have fixed that defect over the 230+ pages" and similar arguments.
The fact that the manuscript looks like a patchwork of strokes of different shades now doesn't mean that it looked the same way when it was just fresh out of the shop. Different inks fade (or sometimes even darken) at a different pace. It's quite possible under any of the explanations above that originally and for a while after the manuscript was created it looked neat with nearly the same shade in all the strokes. It's only with time that some fraction of the ink faded or flaked and another fraction stayed creating the mess we can see now.
The fact that the manuscript looks like a patchwork of strokes of different shades now doesn't mean that it looked the same way when it was just fresh out of the shop. Different inks fade (or sometimes even darken) at a different pace. It's quite possible under any of the explanations above that originally and for a while after the manuscript was created it looked neat with nearly the same shade in all the strokes. It's only with time that some fraction of the ink faded or flaked and another fraction stayed creating the mess we can see now.