Contessa Perdono: why laugh?

I googled this phrase and found two blogposts:

Perhaps the most sublime moment in all of music occurs in the Fourth Act of Mozart's Le Nozze di Figaro

The Count's voice, half moan, half cry, echoes through the silenced auditorium with all the remorse and yearning that the human soul is capable of. "Contessa, perdono", he sings, and the music soars like a wounded bird, then, ashamed of its own presumption, sinks wearily, guiltily back to earth.

In the end, the Count is shamed into begging the Countess's pardon. Contessa, Perdono.The most beautiful phrase in Western music.

I may not agree with the absolute comparative but I see no reason to argue with these heartfelt opinions. It's the 'game changer' in the opera. It's legitimate to ask whether the Count is genuinely remorseful - in other words, it's human to assume that, in time, he will fall back into his sex-pest habits. But he is genuinely remorseful in the moment; he believes himself to be truly so. How do I know? Because the music tells me so.

And yet, when I see this from amidst the expensive seats, there is laughter. To some people, it's a hilarious moment. Actually, I doubt that. Very little in opera provokes spontaneous unstoppable belly shaking laughter. Some situations inspire a ripple of amusement. 

Why do people laugh here? Maybe they are virulently feminist anti-establishment types, more extremely so than me, snorting in derision in the duplicitous male, gleefully anticipating The Reign of Terror. The special undercover feminist revolutionaries who cunningly disguise themselves as smug posh people and sit in the expensive seats at the Royal Opera House. I doubt it.

So why do they laugh? Are they just reading the surtitle screen? I don't understand it. It is worse by several degrees of magnitude to those that give a throaty 'ha ha ha' to make sure everyone knows they've 'got' the joke in a light-hearted funny comedy. It risks ruining the moment for everyone who has been listening to the music, hearing the emotions unfold.

There must be a good reason, because it happens so frequently - I know directly and I've read it so often 

I can't recall 100%, but I'm pretty certain when I saw Figaro in pre-surtitle days, nobody laughed at the Count's line "Contessa perdono!" ... and now audiences seem to find that exquisitely beautiful line something to just roar in laughter at. Anyone have any idea as to why?

and

  I once heard a master coach comment that in a successful production of Figaro, the audience doesn’t laugh when the Count says “Contessa, perdono,” because, though one has little faith in the future, in the moment he truly believes it. In this production, no one laughed.

 and

A good few members of the audience, however, seemed to find hilarious a chair being pushed from one side of the stage. Presumably many of them were the same people who laughed – unforgivably – at the Count’s final plea for forgiveness.