In A one can see that in the entire second part of the Prelude the dotted rhythms in the R.H. part's top voice were devoid of both double dots and demisemiquavers. Chopin marked the first change by adding only a second dot next to the b quaver and a third beam to the following semiquaver/demisemiquaver. In the next ones he would also modify the position of the newly created demisemiquavers with respect to the triplets' third quavers. This confirms that placing the upper voice note vertically aligned with the corresponding lower voice quaver meant simultaneous performance, since hitting the demisemiquaver after the last quaver of the triplet required them to be separated in writing.
Compare the passage in the sources»
category imprint: Corrections & alterations; Source & stylistic information
issues: Corrections in A, Deletions in A
notation: Rhythm