It seems to me that because of the low speed Sully was lucky to have been able to achieve the flare that he did - it was at the edge of having enough manoeuvre capability.
This thread started with the claim being made that it was all caused by the phugoid damping term in the flight control laws. I have no idea of the laws and transfer functions involved in the alphprot law, but would guess that phugoid damping would be a very low order input compared with, say, alpha limit, alpha dot, pitch rate and pitch rate dot for example.
Bearing in mind that the phugoid is a very long period oscillation that is so insignificant to the handling of most aircraft types it is not specifically tested during aircraft certification, unlike the dutch roll.
It is probably fair to say that the vast majority of pilots would have no idea of the phugoid modes of the aircraft they fly, particularly the period and damping ratio of the oscillation.
Perhaps some one can tell me how phugoid damping is important in this accident but it is not during general handling of the A320? Try to provoke the phugoid in an A320 in normal law - it is not possible - I don't know if a phugiod damping term is responsible for this or things like G command, pitch rate demand, SPO damping, and probably a myriad of other inputs to the normal law are.
I don't hear too many A320 pilots complaining about poor handling characteristics in pitch, normal law, because of the very heavily damped phugoid.