The absence of the R.H. slurs in FE (except for the first, under the semiquavers) is most probably a side effect of changes to the layout of the R.H. part. These changes, introduced in print, comprised all instances of this bar (bars 20, 68 and 124), but a slur over the upper voice, which probably should have appeared each time, is only printed in bar 124, owing to the engraver's negligence or Chopin's inadvertence. In the editors opinion the slur was meant to replace the slur in the lower voice, written in A. In GE and EE the slur over the upper voice was also reproduced in bars 20 and 68 (in GE Chopin's inspiration cannot be excluded). Cf. note regarding the L.H. part.
Compare the passage in the sources»
category imprint: Differences between sources; Editorial revisions
issues: EE revisions, Inaccuracies in FE, GE revisions, Authentic corrections of FE
notation: Slurs