How good is your pareidolia?

[Jorge_Stolfi]

How could one retrace strokes with so high a precision

The original characters were traced with strokes 0.2 to 0.5 mm wide, with precision ~0.1 mm.  That is in fact the precision with which most anyone will write or draw with any sufficiently fine pen.  Just try it.  So the retracing did not require any more precision than the original scribing did.

As for the "double strokes" in the second image: if you mean the o, that is not two separate traces, but the normal trace of a quill pen that is running out of ink. 

A quill pen (like 19th century steel pens, and modern fountain pens) has a split nib. The two prongs will spread open as the pen touches the paper, then close when the pen is lifted.  This is what makes ink flow in a controlled amount from the "reservoir" up in the hollow of the quill to the tip of the nib.

But when the "reservoir" gets exhausted, the two prongs create two parallel strokes instead of a single broad stroke.

That o was retraced indeed, but the retracing (even though it was split) covered the original completely.

But maybe you meant the second e stroke in the Sh.  Indeed that is an obvious example of retracing.

In fact, it is almost certain that all the dark writing in that second image was retraced.  

All the best, --jorge