The combination of staccato and legato markings mean that the notes should be separated but not as sharply as a true staccato. Even with the pedal present, the articulation will come across. In this particular case, the pedal markings are also strategic to make the phrase clear.

The fingering comes from Chopin. In the absence of a source explaining his reasoning, I propose what I feel are two reasonable explanations.

1. Using the same finger facilitates -- in fact, requires -- a non-legato touch.
2. Using the same finger also suggests that Chopin wants an evenness of tone across those notes. I base this on the convention that one changes fingers on repeated notes in part to promote a difference in touch.

As long as these musical goals of a non-legato and even touch are observed, the fingering can be modified as best allows you to achieve the sound.

The combination of staccato and legato markings mean that the notes should be separated but not as sharply as a true staccato. Even with the pedal present, the articulation will come across. In this particular case, the pedal markings are also strategic to make the phrase clear.

The fingering comes from Chopin.¹ In the absence of a source explaining his reasoning, I propose what I feel are two reasonable explanations.

1. Using the same finger facilitates -- in fact, requires -- a non-legato touch.
2. Using the same finger also suggests that Chopin wants an evenness of tone across those notes. I base this on the convention that one changes fingers on repeated notes in part to promote a difference in touch.

As long as these musical goals of a non-legato and even touch are observed, the fingering can be modified as best allows you to achieve the sound.

¹ Based on the Preface of the Henle Urtext edition: "Figures in italics stem from manuscript sources, or the first editions, and therefore represent the fingering which has been suggested by Chopin himself." Op. 9 No. 2 is based on the French first edition, with the German edition also consulted (page 123). The particular fingerings in question are given in italics in the Henle score (page 14). Frederic Chopin, Nocturnes, ed. Ewald Zimmermann (1980, Henle).