Flyinheavy;
Could it show a lack of training for this particular situation (1 T/R inop) or missinterpretation of eng contrl system, which btw is rather complex and as such providing traps.
This was covered extensively in the TAM accident thread. Neither manufacturer's thrust lever design is immune to technical or human error. Non-moving thrust levers are not an issue either. Before autothrust all of us flew non-moving throttles that we actually had to physically close at touchdown. There are incidents of not doing that for all types and not just the 320. They are rare, but they have occurred.
All automated systems are complex and are therefore open to technical or human error. I think that stating that such "provides traps" is like saying airplanes provide traps - both statements are trivially true and do not point either to problems or solutions.
Training is a key as I have said a number of times on this and other threads. I have said many pilots are afraid to disconnect the autothrust on the 320 - that is a training issue, not a complexity matter. The airplane flies beautifully in fully-manual flight - it is no more difficult to fly than any other type and no busier - if it is, there is a training/practise problem occuring not a complexity/technical matter.
The other issue is, as Bernd has eloquently stated, no automation can handle all human error. That is indeed where it can get complex. How to determine failure and arbitrate failure in two systems is a case in point. Every solution is attended by other, perhaps less obvious problems. I should think that all those suggested design changes which have been suggested here regarding various perceived system/automation faults have already been vetted by those who do this for a living and rejected for one or another good reason.
In other places I have suggested, not uniquely of course, that because humans are so poor at monitoring over long periods of idleness and that computers never tire, that there are some, not all, areas of normal operation which could be passively monitored with increasing intervention as "normal" degrades to abnormal. I know that there are significant problems with this approach and know also that the Airbus has already taken this approach in some, but not all, areas of aircraft operation.