In GC (→GE1) and EE there is no 
returning f
at the beginning of the 2nd group of semiquavers of the introduction, which almost certainly corresponds to the notation of [A]. It is a very typical mistake of Chopin – cf., e.g., the Nocturne in Cminor, Op. 27 No. 1, bar 83, or the Impromptu in A
major, Op. 29, bar 71. The sign was added in the proofreading of FE, most probably by Chopin, as well as in GE2 (→GE3).
Compare the passage in the sources»
category imprint: Interpretations within context; Differences between sources
issues: Errors in EE, Omissions to cancel alteration, Errors in GE, GE revisions, Authentic corrections of FE
notation: Pitch