All four examples involve threats - one party threatening to punish another unless the other party obeys some rule - but the last threat (threatening to increase existential risk contingent on acts of forum moderation) sticks out as different from the others in several ways:

1. Proportionality. The punishment in the other examples seems roughly proportional to the offense ($500 may seem a bit high for one album, but is in the ballpark given the low chance of being caught), but over 6,000 deaths (in expectation) plus preventing who-knows-how-many people from ever living is disproportionate to the offense of deleting forum comments.
2. Narrow targeting. Most of the punishments are narrowly targeted at the offender - the offender is the one who suffers the negative consequences of the punishment, as much as possible (although there are some broader consequences - e.g., the rest of the forum is deprived of a banned poster's comments). But the existential risk threat is not targeted at all - it's aimed at the whole world. Threats to third parties are usually frowned upon - think of hostage taking, or threats to harm someone's family.
3. Legitimate authority. There are laws & conventions regarding who has authority over what, and these limit what threats are seen as acceptable. Threats can be dangerous and destructive, because of the possibility that they will actually be carried out and because of the risk of escalating threats and counter-threats as people try to influence each other's behavior, and these conventions about domains of authority help limit the damage. It's widely accepted that the government is allowed to regulate driving and intellectual property, and to use fines as punishment. The law grants IP-holders rights to sue for money. Forum moderators are understood to have control over what gets posted on their forum, and who posts. But a single forum user does not have the authority to dictate what gets posted on a forum.
4. Accountability. Those with legitimate authority are usually accountable to a broader public. If citizens oppose a law they can replace the legislators with ones who will change the law, and since legislators know this and want to keep their jobs they pay attention to the citizens' views when passing laws. Members of an online forum can leave en masse to another forum if they disagree strongly with the moderation policy, and forums take this into account when they set their moderation policy. But one person who threatens to increase existential risk if his preferred forum policy isn't put into place is not accountable to anyone - it doesn't matter how many people disagree with his preferred forum policy, or with his proposed punishment.

I'm not entirely in agreement with the first three threats, but they're at least within the bounds of the kinds of threats that are commonly acceptable. The fourth is not.

The common misunderstanding from these comments is that they didn't click on the "precommitment" link and read the reasons why the precommitment reduced existential risk.

If I ever do this again, I'll make the reasoning more explicit. In the mean time I'm not sure what to do except add this comment, and the edit at the bottom of the article for new readers.

In that case they should present their evidence and/or a strong argument for this, not attempt to blackmail moderators.

Laws are not comparable to blackmail because they have process behind them. If one loan individual told me that if I didn't wear my seatbelt, he'd bust my kneecaps, then that would be blackmail. Might even qualify as terrorism, since he is trying to constrain my actions by threat of illegitimate force.

A lone individual making a threat against the main moderator of a site if he uses his discretion in a certain way is indeed blackmail/terrorism, particularly when the threat is over a thing substantially outside the purview of the site, and the act threatened is on its own clearly immoral (e.g. it'd be legitimate to threaten leaving the site, or reposting censored material on a separate site). As it stands, it's an attempt to force another's will without any semblance of legitimate authority, which seems to qualify as " clearly wrong."

Moved post to Discussion section. Note that user's karma has now dropped below what's necessary to submit to the main site.

Do you understand the math behind the Roko post deletion?

Yes, his post was based on (garbled versions of) some work I had been doing at FHI, which I had talked about with him while trying to figure out some knotty sub-problems.

What do you think about the Roko post deletion?

I think the intent behind it was benign, at least in that Eliezer had his views about the issue (which is more general, and not about screwed-up FAI attempts) previously, and that he was motivated to prevent harm to people hearing the idea and others generally. Indeed, he was explicitly motivated enough to take a PR hit for SIAI.

Regarding the substance, I think there are some pretty good reasons for thinking that the expected value (with a small probability of a high impact) of the info for the overwhelming majority of people exposed to it would be negative, although that estimate is unstable in the face of new info.

It's obvious that the deletion caused more freak-out and uncertainty than anticipated, leading to a net increase in people reading and thinking about the content compared to the counterfactual with no deletion. So regardless of the substance about the info, clearly it was a mistake to delete (which Eliezer also recognizes).

What do you think about future deletions?

Obviously, Eliezer is continuing to delete comments reposting on the topic of the deleted post. It seems fairly futile to me, but not entirely. I don't think that Less Wrong is made worse by the absence of that content as such, although the fear and uncertainty about it seem to be harmful. You said you were worried because it makes you uncertain about whether future deletions will occur and of what.

After about half an hour of trying, I can't think of another topic with the same sorts of features. There may be cases involving things like stalkers or bank PINs or 4chan attacks or planning illegal activities. Eliezer called on people not to discuss AI at the beginning of Less Wrong to help establish its rationality focus, and to back off from the gender warfare, but hasn't used deletion powers for such things.

Less Wrong has been around for 20 months. If we can rigorously carve out the stalker/PIN/illegality/spam/threats cases I would be happy to bet $500 against $50 that we won't see another topic banned over the next 20 months.

Yes. THIS IS NOT CENSORSHIP. Just in case anyone missed it.

May I at this point point out that I agree that the post in question should not appear in public. Therefore, it is a question of the author's right to retract material, not of censorship.