My comments were less to do with the risk of scalding but more with the effect on skin barrier, and thus on the potential for damage to health from washing in hot water. Water has long been identified as a skin irritant by dermatologists and wet work is the most common cause of occupational irritant contact dermatitis. With the current encouragement for frequent hand washing due to Covid-19 there has been an increase in cases of irritant contact dermatitis. So anything that increases the damage that this causes is something that should be avoided. In my experience the cost of fitting temperature control valves is insignificant compared with any increase in skin damage that hot water (not scalding) will cause. Moreover, when fitted it is often found that they reduce the comsumption of hot water and hence reduce the cost of heating it. So they can even be cost saving.