I just figured out what these notes remind me of. I used to proofread for a court reporter, and this code reminds me of the raw code printed on old fashioned steno tape. It's not the same code, but might be a similar system but with different letters.
Each sound is represented by a combination of between 1 and 4 letters (out of a possible 7) The code uses a different combination (and mostly different letters) depending on whether the sound comes at the beginning of a syllable or the end, with the characters representing the vowel sounds in the middle. The choices for the beginning of the syllable are STKPWHR and the choices for the end are EUFRPBLGTSDZ, in that order. For instance:
............................at beginning....................at end
sound of G =..............TKPW...........................G
sound of N =,,,,,,,,,,,,,,TPH.............................PB
The vowels on steno tape are similar to the consonants, but they are obviously vowels, unlike the code or cipher on RM's notes.
Anyway, RM's notes are not steno notes, but they might use this kind of complicated system, with those many n's marking the places between syllables or something like that.
