According to Sune Foldager:
More useful and maybe easier to implement would be "hardwrap on save", where everything currently soft-wrapped is hardwrapped when saved into the file. Of course I guess it would still need a counterpart 'unwrap on load' to really work :p.
You can workaround by using a command like fmt(1) or par(1) on the document or a selection but it is more cumbersome than just typing and the editor DTRT.