Decentralized authority

Publicly shun people. You're a rule breaker? You've been shunned by society and people who associate with you will be known associates of the shunned.

Short answer: The community.

In small contexts, a mutual understanding is sufficient. There are "Radical Therapy" groups with no central therapist who decides who talks how much but instead have rules like fixed times for each person. I don't think people will break these rules but exclusion is always an option with very intransigent people.

In bigger contexts like the Commons, people deliberate on their own rules. Minor transgressions will have minor consequences and the worst is – again – exclusion. People are more willing to stick to the rules and watch others if they were part of the process that created the rules. If you want to dive deeper, I remember a podcast episode by SRSLY WRONG and a YouTube video by Andrewism about The Commons or The Tragedy of the Common.

free (dis) association

it's an archipelagic confederation, so yes!

That's a very good question. It's as anarchist as modern social media gets.

The thing is the moderators. In an anarchist utopia, they would take turns, be recallable and have to justify their decisions.

The last point is true for some instances but not all (think of the vegan cat food debate on .world verses how .ml blocks voices critical of China and Russia).

The other two points – to my knowledge – barely happen. This isn't a huge problem, as I said, it's as anarchist as social media comes. But it contains the risk of a centralized power. Sure, you can always leave the instance (even easier than on mastodon where you lose your followers) but this resembles the Libertarian "freedom" to choose your oppressor. Internal equality is very important.

This isn't to criticize Lemmy. It's overall very good and as anarchist as realistically and practically possible. But to showcase the anarchist ideal of councils and to spotlight the minor flaws we should be aware of, even if there is no perfect solution.

Well you learned the wrong here, anarchy isnt the absence of authority it's the absence of hierarchy.

Some systems are clearly hierarchical, capitalism, dictatorship, feudalism.

Now I have a hard time imagining how you would enforce certain laws, or rules without authority.

I'm not sure what makes you think of (right wing) libertarians. I specified the absence of authority. Libertarians are fond of the idea of voluntary contracts – or let's rather call it voluntary authority – which in effect is never voluntary. You can choose for whom to work but there is a ruling class you have to work for. All you can do is choose your oppressor.

Free association among equals on the other hand is a very common idea among (left/socialist) anarchists and I think very early on. You can choose and leave the community you belong to.

Is it ironic if they play monopoly?