Make sure the three instances of special fire effects stay
synchronized in the future by moving the relevant code into its own
routine.
Shouldn't fire vortices and fire elementals also yield "already
on fire"? How about ice vortices "melting"?
Can't push boulders through iron bars; traps can't roll such through either;
likewise for objects thrown by monsters.
Thrown objects susceptible to breaking might do so when they hit iron bars.
Assorted monsters can pass through iron bars; ditto for polymorphed character.
Attempting to dig iron bars will wake nearby monsters instead of yielding
"you swing your pick-axe through thin air".
Autodig won't accept iron bars as candidate location.
