.. Do you hear in both videos the person is playing with D#? ..
Wow, you're right, thanks for catching that! Playing it on my own piano it sounded better with F# though. I wanted to use those youtube videos mainly just to show the score (and because I finally figured out how to embed youtube videos which I think is really cool!)
When learning a new piece I sometimes compare scores, for fingering suggestions, etc. I went back to
https://imslp.org/wiki/Nocturne_in_C-sharp_minor,_B.49_(Chopin,_Frédéric) where there are 5 scores.
The Misc. Notes for the 4th one says:
The original Chopin manuscript has an D# as the first and fifth notes of the left hand in bar 8, not F# as shown in this version.
The Misc. Notes for the 5th one:
Some editions show D# as the first and fifth notes of the left hand in bar 8: this must be a mistake, since it does not sound right harmonically...
Finally under General Information, Misc. Comments it says
Main soundtrack of the 2002 film The Pianist. A comparison of the piece played by Adrien Brody in the film with the score above will illustrate some differences. This is because the PDF version provided above is a slightly simplified version that contains some modifications from the original Chopin manuscript. The Henle Urtext versions, considered by many to be accurate, appears to contain many editorial modifications from the original manuscripts, including the F# in place of the original D# as mentioned in the miscellaneous notes above. The Leon Erdstein edition appears to be faithful to the original manuscript, for this particular piece at least. Finally, the Paderewski editions of Chopin, considered by some to be spurious, contain a commentary at the back of the volume which details the sources with any known modifications clearly listed.
Didn't notice these comments at first - I wanted to get right to playing the piece. But I include them here for completeness, or in case anyone else is interested.
On the one hand, I'd like to play it the way Chopin wrote it. On the other hand I think it sounds better with the F#.