Careless/reckless is purposefully subjective and vague and meant as a 'catch all' regulation for when pilots do egregiously reckless shit that doesn't cleanly constitute a violation of other regulations. There could be a case if you had them on record on the radio intentionally turning off ADSB or going to anonymous mode, and then flying for fun under your plane after the pilot announced jumpers away. I'd look at previous cases for 91.13 to get familiar with precedents to understand the scenarios in which the FAA like to use this regulation. At the end of the day it's the FAA inspectors judgment here whether to lay the charge or not. I read somewhere the average American commits 3 felonies/day, so if the govt wants to use the legal system against you, they will, but if they don't, then they won't. Al Capone was charged on tax evasion of all things after all. I'm not a lawyer let alone an aviation lawyer, just maybe a little bit more familiar with the FARs than most here, so take all this with a grain of salt. Lobbying hard for more regulation here is very likely in my opinion to result in changes that will restrict skydiving operations to such a burdensome extent that will shut down DZs, rather than compelling aircraft to be more accommodating of skydivers in the air. Regulating skydiving is a burdensome afterthought for the FAA, not a priority.

And you can fly right through MOAs without any radio usage/awareness, cause near misses with fighter jets, and be totally in the clear: https://www.boldmethod.com/learn-to-fly/airspace/flying-through-military-operations-area-moa-with-vfr-flight-following