"This work is still being done on platforms like Facebook and Reddit. But unlike the sysops who enabled the flourishing of early online communities, the volunteer moderators on today's platforms do not own the infrastructures they oversee."
Volunteer moderators on Facebook. Perhaps I am misunderstanding this sentence. There have been a few documentaries showing how Facebook does moderation. It is done by low paid workers, e.g, in the Phillipines or Ireland, not volunteers. The first line moderation work is contracted out.
There is actually profound lack of moderation because (a) moderators are overwhelmed and cannot keep up and (b) the priority of Facebook is what attracts the most traffic ("engagement") not meeting standards. If some group page is getting lots of traffic then it goes into a special category. The moderators cannot delete it without approval from FTEs at Facebook. The number one priority is traffic,^1 not upholding any standard for content. Any standards enforced are only created in response to complaints. Section 230 shields Facebook from most of the potential legal liability.
1. Under the guise of soundbites such as "connecting the world" and "giving everyone a voice". People can be connected and have a voice and still only "engage" with Facebook periodically/sporadically. Overall, low traffic. But without both high traffic and ads, Facebook's days are numbered. Hence, ever more indignant, angry, extreme content is required to draw "engagement".
Edit: Thank you @LamdaComplex. I think that explains it.