> > If this line is followed, I'd recommend rebinding one of the transpose
> > commands (transpose-lines, perhaps) to swap the TO and FROM. Having to
> > manually kill and yank would be a very cumbersome way of reversing the
> > replacement.
>
> Good idea.  However, `transpose-lines' doesn't seem to fit semantically.
> But perhaps you proposed it because other transpose-* commands might be
> useful in the query-replace minibuffer inside the FROM or TO part.

Yes, I figured transpose-lines is the least useful of the transpose
commands when it comes to query-replace input. But transpose sexps is
probably almost as useless and might feel more intuitive.