The contrasting dynamic indications in bars 5, 9 and 13 were most probably added to FC by Chopin, as were many other markings (e.g. dynamic hairpins or accents). However, one has to emphasise that these marks, although their shape is the same as of some undoubtedly Chopinesque ones (e.g. 
in the autograph of the Scherzo in B
minor, Op. 31, bar 25, 
in the autograph of the Etude in A, Op. 25 No. 1, bars 9 and 22, 
in the autograph of the Etude in F minor, Op. 10 No. 9, bars 29 and 33 or in the later autograph of the Polonaise-Fantaisie, Op. 61, bar 1), are also very similar to the Fontana ones. The fact that they could have been written in Chopin's hand is indicated by, e.g. their more delicate, as if pale notation – cf. the analogous markings in the Mazurka in B minor no. 2, written certainly by Fontana.
In bar 5 was added in FES, which, to a certain extent, confirms Chopin's intention to contrast the particular theme phrases, dynamically and probably also expressively.
See also bars 37-45.
Compare the passage in the sources»
category imprint: Differences between sources
issues: Annotations in teaching copies, Annotations in FES, Authentic corrections of FC
notation: Verbal indications