Hi Diver7mmwet,
Not a badly thought out article except for the one piece you are missing that is the legal bite of it all.
In reading the DOT, CGA and OSHA documents regarding storage and handling of high pressure gases the issue is safety and legal liability. Just like every other part of our sport it comes down to mitigating the risks involved. If you are refilling for yourself the liability risks may be limited but the dangers of a explosion are real not imaginary. If you are refilling for commercial gain the exposure to risk does increase. Certification and training is about increasing your shielding from liability risk. So if you are a do it yourselfer and your fill station is isolated to the point that explosive damage would be limited to your own property then that is your risk alone. If your fill station is near enough to neighbors to risk their person or property you had best consider that and if your liability insurance would cover you should an incident occur. If you are engaged in anything beyond for yourself it doesn’t matter how isolated your fill station you are always at increased liability risk. Not just from explosion but from questions of service or fill quality should anything happen to a diver using a tank that you serviced in any way. So you may question the validity of the services involved with tank inspection and the certifications required to do so but if you ever get caught up in litigation you’ll wish you had adhered to an accredited program such as PSI/PCI.