>How many new truly independent, individual-run forums can you name today?

Almost none, but it's due to a lot of complicated factors and not just the direct risk of user content.

Take moderation of content that won't get you banned by your ISP. It sucks. Nobody in their right mind would want to do it. There are countless bots and trolls that are going to flood your forums for whatever cause they champion.

Then there is DDOS floods because you pissed off said bots and trolls. This can make the forums unaffordable and piss off your ISP.

But even if nothing goes wrong, popularity is a risk in itself. In the past there was stuff like the Slashdot effect where your site would go down for a while. But now if your small site became popular on tiktok for some reason 20 million people could show up. Even if your site can stand up to that, how will you moderate it? How will you pay for the bandwidth?

Oh, and will you get any advertisers because of said user content? How are you going to pay for the site?

Oh, also you're competing with massive sites for eyeballs, how are you going to get actual users?