At the end of the Chopin Nocturne No. 13 in c minor, Op. 48 No. 1 there is a very dramatic return of the first subject with an underlying torrent of triplets. When there are eighth-notes in the melody they are written on the first and last notes of the underlying triplet (as apposed to writing it three against two). Mostly everyone that I have heard, plays as it is written, not three against two.
See 4:15:
I have been told that it is a "Chopinism." In my opinion, it would not have been too difficult to write a quarter and an eighth in triplets if that was the rhythm that Chopin wanted. The only pianist that I have heard that plays the eighths two against three is Rubinstein:
See 4:23
So what do you think? "Chopinism" or two against three? or is there a third option...?