AfterDark
Contributor
I see no harm in using the 1/4 turn to back off from fully open. It signals to someone else who may be rechecking the valve that it is indeed "open" to some degree. Further checking will soon indicate whether it is nearly fully open or nearly fully closed. Someone checking a fully open valve may mistake it for a closed one and give it a good reef which may jam it open. Not always dangerous when diving with a single tank and K valve (inconvenient maybe) but may be problematic in a doubles or Y/H valve combo when a needed shut down cannot be performed. BTW, I have actually seen people struggling to open an already opened valve.
That's a sure fire way to get yelled at by me. Nobody touchs my valves after I turn them on, unless I ask them too.