I draw the line on discoverability. Reddit? Public. Hacker news? Public. 4chan? Public. Facebook and Instagram are also public with a slight caveat, private accounts will be considered private, otherwise public. Even ye old public forums are considered public.

Discord and group chats will be considered private. Basically anything that requires an invitation / permission to view their content is considered private. To your example, I'm not sure if J6 members were organising publicly themselves. If the FBI wanted to, they could easily infiltrate these groups as an anonymous member themselves, so I don't see a contradiction there.

Legislatively, it means that platforms will be held responsible for their public content, which I think is fair. If there are too much content to moderate, it's up to them to find solutions. I hear rumours of a promising automating tool called LLMs.