Bursting into flames shouldn't be possible, that's a LOT worse than a "dud". (Assuming parent isn't exaggerating)

Not exaggerating. I had it for a little over a year. I used it in my bedroom. As usual I started it going and then went into my bathroom to brush my teeth before bed. Partly through brushing my teeth I smelled something burning. I came out and saw the humidifier in flames.

It does raise the question of certification and product safety in general, there are so many electrical devices that probably don't meet Western safety standards. A humidifier is basically a heating element in a plastic housing, it should be engineered with safety features (overheating protection etc) so it shouldn't be able to just catch fire, someone clearly didn't do their job properly at some stage. I wonder how product recalls work with that sort of thing.

I don’t think I would make that leap about falling short of Western safety standards.

All electrical products sold in the US are legally required to be NRTL certified (according to US standards). Levoit is ETL certified.

Non certified products are seized by customs or recalled from the market.

It’s very unlikely and I agree, not acceptable, but any household appliance with a heating element has a nonzero fire risk. I read that for UL certified humidifiers the incidence rate is 1 in 100k, similar to fans. The seems worryingly high.