The 
indication appears in FE (→GE,EE) what urges to consider it a correction by Chopin. However, the comparison with the parallel passage in bars 30-33 rises doubts as to wether this sign was really intended – both four-bar sections have identical principal dynamic indications (, 
, cresc.) but there is no equivalent to the sign in question. We can then suspect a misunderstanding of a 
sign (quite frequent in FE – cf. bar 54) or even an outright mistake by the engraver overlooked by Chopin during proofreading. For these reasons we retain the A version in the main text, while regarding the vesion of the editions and its suggested interpretation as alternative readings.
Compare the passage in the sources»
category imprint: Interpretations within context; Differences between sources
issues: Authentic corrections of FE
notation: Verbal indications