Nope, logical not in I6 is ~~. ~ is bitwise not.
Yes, of course until is much nicer than while no. But every so often when making a compound conditional an actual logical not is useful. Unfortunately, there’s no good English equivalent to “not” and while the compiler will accept To decide if not (c - condition): [...], that seems like asking, nay, begging for trouble. So I borrowed “no” from Spanish; in English it’s somewhat awkward, but does convey the correct meaning. (Though if one wanted to burn it all to the ground, one could use To decide if ! (c - condition): [...].)