IMO (not a scientist), moon dust is basically pulverized glass, only without the benefits of weathering and erosion. So think of lots of microscopic sharp, abrasive, shards of finely pulverized volcanic rock and obsidian. Get that stuff anywhere near a mucous membrane - eyes, nose, mouth, throat - and it’s going to irritate you. At the same time, it’s pretty much intert; well, at least the parts that don’t instantly react to oxygen or humidity that is. My guess is that Schmidt is just a little more sensitive to the physical sensation of it, or perhaps he rubbed his eyes with a glove by accident, giving him an extra big dose.
And for the uninitiated, it’s well documented that everyone in the lander was physically exposed to moon dust. There was no airlock on the lander, so every excursion resulted in bringing whatever was on the suits right into the cabin. They reported that it “smelled” like burned gunpowder, so they were at least all inhaling the stuff.
Watching people repair old electronics on Youtube has opened my eyes to the realities of real-world electrical engineering. In short: it’s all about tolerances.
A power supply may have a nominal voltage of 5V, but anything from 4.8 to 5.2 is a-okay. Why? Because your TTL components downstream of that can tolerate that. Components that do 5V logic can define logic zero as anything between 0 and 0.8 volts, and logic one as low as 2 volts. That’s important since the whole voltage rail can fluctuate a lot when devices use more power, or draw power simultaneously. While you can slap capacitors all over the place to smooth that out, there’s still peaks and dips over time.
Meanwhile, some assembly lines have figured out how to aggressively cost-reduce goods by removing whole components from some circuits. Just watch some Big Clive videos. Here, the tendency is to lean heavily into those tolerances and just run parts hot, under/over powered, or just completely outside the published spec because the real-deal can take it (for a while). After all, everything is a resistor if you give it enough voltage, an inductor if the wire’s long enough, a capacitor if the board layout is a mess, and a heatsink if it’s touching the case.