It's my understanding that any accidental showing on the treble clef also applies to the bass clef unless indicated otherwise, correct?
For measure 13 of Chopin Nocturne Op. 9 No. 2, my Henle Verlag urtext (the image here is from a video but has the same notes as my Henle book) shows the natural sign for the note A in the treble clef, and no accidental shown in the bass clef. Shouldn't the left hand play the natural A, too? But I watched three videos and they all played Ab on left hand. (One video by Paul Barton used a score that has a flat sign next to the 2nd occurence of the A note in bass clef, but he played both A as Ab.)
Having said the above, I would tend to play Ab on left hand, too, since up to that part all the previous cases of the same chord combination had Ab. However, the Henle truly didn't have the flat symbol in the bass clef.
(Maybe it's no big deal? am I being too pedantic? ;-))
