In tiles, clicking on an unsafe monster will walk you one square closer, but clicking on a safe monster (i.e., plant) does nothing. _click_travel() in tilereg.cc calls start_travel() and then returns CK_MOUSE_CMD, but this has no effect.
That's because travel doesn't work if the target grid is occupied by an immobile monster. "X." doesn't work, either.
For tiles, at least, it would be nice to get it to work.