The problem is that somebody took it on themselves to play with somebody's equipment during a dive WITHOUT asking
This whole thing is a perfect example of the Incident pit where a series of event leads to something greater
A better (IMO) write up of the incident would be this as a learning exercise
1. New BCD had malfunctioning inflator - sent to shop for repair
2. Shop delivers BCD to owner on day of dive, untested.
3. The dive group consists of 2 dive couples Couple 1. She
(Diver 1) OW approx 100 dives, He
(Diver 2) Rescue diver approx 100 dives Couple#2 Divers 3 and 4) a pair with approx 20-30 dives each
4. Couple 1 found the Inflator to still be malfunctioning but chose to dive it disconnected.
They did not inform the other couple they were diving with about the malfunctioning inflator, nor their decision to dive with it disconnected
5. During Dive Diver 3 notice Diver 1's LPI hose disconnected and try to assist
without asking (Diver 1)
6. The Diver 1 doesn't notice someone tampering with her gear - (or does but doesn't stop them)
7. On connection Diver 1's BCD has runaway inflation, she has a fast ascent, but does not disconnect LP hose, nor try to arrest ascent by dumping air. (As taught in PADI OW Course)
8. Diver 3 tries to stop ascent, but loses grip
9 Diver 2 (Rescue Diver) is too far away from his buddy to be able to render assistance, or notice Diver 3's actions
And so:
So remove any of the first 4 points and point 5 wouldn't of happened.
With Diver 3's actions it shouldn't have become a problem if Divers 1 & 2 have been more practiced with their relevant training
If I were the DM on the boat, I'd for sure chat to Diver 3 about his actions, but Diver's 1 and 2 would also get spoken to, about their failings - Especially Diver 2 a Rescue Diver - because all this is covered in his course in both theory and practical skills and he should have done more
In the event its nothing more than a minor scare, and a few bruised egos, which provide a learning experience for all, especially that all training is useless if you forget the knowledge and skills you've learnt