As a result of comparison of the indications of FE in bar 646 and 648-650, we interpret the 
mark in this bar as a long accent, referring to both hands. The mark was placed lower also in GE and EE. The overspread mark in GE3 results from the actions of the reviser who considered it to be diminuendo only, since he did not figure that it could be an accent; it is possible that he wanted to align that diminuendo with the descending part of the passage.
Compare the passage in the sources »
category imprint: Differences between sources; Editorial revisions
issues: Long accents, Placement of markings, GE revisions
notation: Articulation, Accents, Hairpins