The only down side was it kept the moderators of the web site and other nazi’s from controlling what you saw.

Bots got better, they spam faster than you vote. They vote faster too.

Also brigading, but I can’t know how harmful it would be in a botless world.

That sounds fairly self contradictory to me.

If someone comes and fills your community with spam, you can’t realistically expect potential new users to manually block every spammer. They’ll just leave. And you’re effectively silenced. Spam may not be the correct term, since disruptors don’t necessary act in bad faith. But they shouldn’t have the ability to silence you regardless of their intentions.

Circlejerks? Well, if a person doesn’t care about the truth and only wants to feel social approval, what can you do? Discussing new ideas would endanger their goal, so they won’t participate in a discussion no matter what. You could try to provide some free approval to sate their hunger, but it’s harder than it seems.

Reddit would shadowban you. Or adminban you.

Here, you know you were banned and can act accordingly.

The ability to start your own community ensures that everyone can speak. The ability to remove malicious actors from your community ensures that everyone can speak uninterrupted.