To go back to George's questions:

When you let one rip, is the damage repairable?
Something to do with a stitch in time, I guess.

Why is it that the noisy ones are often less smelly, but the silent ones are the real killers?
The noise level is due to the pressure of the gas. High pressure 'events' are usually caused by ingesting air with food, or consuming fizzy drinks etc - mostly CO2, nitrogen & so on, which don't smell much. Low pressure farts often result from bacterial decay in the gut, and contain organic 'aromatics' and sulphides, which don't smell at all - they stink!

Is there a foolproof way of telling the dry from the wet ones in advance?
I believe the operative term here is 'in advance'. No - life is full of surprises.

Why is a "rumbler" more satisfying in the presence of piles?
Piles of what?

Did La Petomaine exist? Was she a real person? And was she "natural", or pump-assisted (as claimed by the eponymous film with Leonard Rossiter)?
Never let the facts get in the way of a good story.

Andrew