The lack of sempre forte nad marcato indications results certainly from an oversight by the engraver of FE. He omitted all verbal indications in the line comprising bars 156-160.
The designation sempre forte is placed in the sources around the middle of the bar, so that its beginning falls under the third (A→GC→GE) or fourth (EE) semiquaver. In the editors' opinion it is probably an instance of Chopin's mannerism of writing markings inside the domain of their application, hence we put the indication at the beginning of the bar in the main text. It bears no practical implication anyway, for the indication basically confirms the dynamics effective in the entire Presto.
#Wa replaced the word forte with the 
sign.
Compare the passage in the sources »
category imprint: Differences between sources
issues: Errors in FE
notation: Verbal indications
