I never had an issue, just barely tighten and loosen repeatedly if one snags. Like quarter or half turns not multiple full turns. And soot will fall off hopefully. Carbon will get blown out, its broken tips that are the worst but I don't recall people breaking the tips themselves when its a good brand like motorcraft beru, my bosch came right out too. A few had soot but not rushing, they came out just fine. I may have used pliers/locks to twist after they unthreaded too but its been ages.
I've seen some gore of tips getting embedded in pistons, but can't recall catastrophic failures. Either the piston merges with them or they clear the valves usually, although I'm sure you could bend a valve if it gets caught between them too. Anyone else know of instances?
Oh and if you do drop crud in the precup you can remove the injector, put a shop vacuum on injector hole and air compressor in the glowplug hole and get it out. Some people will rotate each piston to top per plug they do but thats a lot of extra work. Only you can value your time, so you have to choose between probably safe enough and better safe than sorry. I never had the time to fuss with spraying plugs multiple days or rotating the block per glowplug. But crap happens too. You could always rotate only on a stubborn plug to split the difference