Another issue that I just noticed is that the beginning is marked "mezza voce", medium voice. This should be interpreted dynamically as mezza forte, with a forcefulness that is almost exclamatory. Note that there are rests between those two quarter notes (mm. 1, 5, 17, 49, etc.) which also supports this assertion as well as the octave and octave chords in the accompanying LH. Further, m4 is marked stretto which further implies this character, with a rushing force.
This issue has bothered me for several years because every single performance I've heard of this nocturne starts softly, but the way it is written doesn't support such an interpretation. And just trying it now with the exclamatory interpretation, it sounds much, much more in line with the intended character.