This is not a twin engine or even a single manufacturere issue, it's an all engine issue.
It's a form of water that exists at altitude that can turn into ice inside the engine operating at altitude. It's impossible to keep all ice outside of the engine, so it was anticipated that only moderate amounts would form at any time and when shed would be harmless to the engine. the idea behind the icing tests and certificantion requirements was to demonstrate that continuous operation in the worst icing conditions (for the aircraft) would be of no concern to the engines.
Now they have identified a form of precipitation that is actually worse for the engine then the aircraft, mostly because of the altitude and the work cycle that the engine is operating in.
From my read of the WSJ article two problems can result.
Ice can build internally and when shed it permanently damages the higher RPM aft stage of the compressor. (I understood from the article that this did happen to some RR engine models)
Ice can shed and disrupt the fuel air ratio in the burner resulting in blow outs of the flame. (GE some models and P&W some models)
My understanding is that while the mechanical damage to the blading is permanent, the effects are mostly to the stability or surge margin of the engine and can be mitigated for the remainder of the flight by so called babying of the engine.
The blow out of the burner is also recoverable, by auto-restart features in the FADEC or of course the more intense workload of an inflight restart within the relight envelope. Taken together the fleet has been safe todate. However the level of safety is in question.
What now needs to addressed is how well do these mitigation features work and how many of these events will truly continue to be safe using these extra crutches.. The FAA is now faced with trying to come up with a defined level of capability against this newly defined threat. As in all environmental encounters the capability must necessarily consider a balance between the technically feasible level of capability of the product and the need for a corresponding degree of avoidance of the encounter.
The WSJ article did not define the problem to this depth and that is what the FAA must do. The FAA can not do this by themselves and must engage expertise in both the engineering of the engine designs (operability, FADECs etc.) but also the pilots, Radar, ATC and weather geeks on the avoidance side.
In the short term tweaking engines and operating procedures is simply minimization and not elimination of the risk and in my view not really measureable except by counting number of events per year worldwide (which is outside of the view of the NTSB) On the other hand new certification standards typically won't address today's problem for 10-15 years so we are going to have to live with this newly defined risk. Please do not misunderstand me, this is not a new safety risk (it's been there all along) it is simply now a newly defined risk to be recognized and addressed.