It also doesn't feel right to me when I learned it for the first time. But if you know that "=" means "almost equal" when doing float comparision, it is very convenient in practical use. For example, if we want to compare two float variables. In Red:

  if float-1 = float-2 [
      ; do something
  ]

In other languages:

  if (float-1 - float-2) < EPS {
      // do something
  }

Obviously, Red's way is more natural and readable. :)