The ransom note itself, the letter 'f' in 'follow our instructions' pg 1 para 1 its easy to see something unusual here. The top vertical segment doesn't line up with the bottom, and the right horizontal segment doesn't line up with the left. This is not the result of one line crossing another. This is more of a scribble. The pen never left the paper on this character, IMO.
Not a smudge.
And another thing: In the comparison, the curves that predominate PR's side is completely absent on the RN author's side. Is the RN author not able to create a curve or what? The "M' that PR wrote is totally different than the "M' written by the RN author.
Lets face it, there are big differences between the two handwriting styles. RDI is using nervousness, opposite handwriting, and disguised handwriting claims to explain these big differences.