Originally Posted by
runcible
I follow where you're going with this. Nevertheless, if it's worth taking the effort to confront and\or remove the habit, I don't think "gotcha" moments on the firing line are the best way to about it.
If using a live blade, as seen other places; then there is a very real chance that someone is going to very appropriately point a gun at someone that would rather not have such a thing happen.
If using a training blade; then there is the question as to whether or not the shooter remaining faced downrange while verbally querying the person behind them is really appropriate given proximity and having just fired at a target (or notional aggressor). Another place has described using a similar prompt to have shooters reholster, pivot, and verbally challenge the knife bearer; and I don't know if that's an improvement.
If it is a worthy subject for training, I don't know that the live-fire range is the appropriate venue for it; but your mileage may very, and you may work in different realms than I.