First rappeller to the ground: untie stopper knots
Does your rappel end on the ground? Here's a quick task for first person down: untie any stopper knots in the rope.
Once you’re on the ground, stopper knots are no longer needed. If the first person unties them as a regular habit, it eliminates the possible BIG problem of pulling a knot up out of reach when you pull your rope.
Very simple solution for a very common problem!