Yes, ~f means the same as no:f. So far I like the brief and distinctive look of negated functions thus: ~foo. But since potential symbol-syntax chars are rare, I might use ~ for something else one day if negated fns turn out not to be too common. There are currently only 9 in news.arc (1410 LOC).
Edit: Looks like there could be 4 more. Most of news.arc was written before ssyntax, so it's not maximally up to date.