Here and in bar 55 we give in the main text a non-slashed grace note after FE, which seem more reliable in this case. It is true that French editions included inaccuracies in grace notes, but Fontana would very often change non-slashed grace notes to slashed ones (cf. the description of FC in the Preludes, Op. 28). This situation occurs twice in the Mazurka, and in both places FE feature a 
, although almost all the remaining grace notes in entire opus 30 are reproduced there as 
(except bar 80). According to us, it guarantees the authenticity of this notation. As a matter of fact, the notation is probably of no significant importance in practical terms, since the grace note merely indicates that the trill is supposed to begin from the main note.
Compare the passage in the sources»
category imprint: Differences between sources
issues: Notation of grace notes, Non-slashed grace notes, Inaccuracies in FC
notation: Ornaments