Passenger here -- heard it a few times, never figured out the rationale behind applauseworthy landings and not.
The most interesting case of passenger applause was a CY A320 on final to FCO. Pops through overcast and decides to go around, firewalls the engine and pulls up and hard to the right. Wham! #1 compressor stall, the whole airframe shakes like it's been hit with a baseball bat, flames shoot out both ends of the engine.
Immediately, the whole cabin broke out in thunderous applause.