Good point, my implicit assumption is that, unlike the classic forums of my youth, forums in the post-LLM age will want to adopt the "tree of invites" model (e.g. how lobste.rs does it) rather than allowing unrestricted write privileges (read privileges can still be public). This creates a localized web of trust that will be mostly manageable at medium scales; ban or revoke invite privileges to any users whose invitees turn out to be bots or sockpuppets.