I've forged my own understanding of the levels, picking and choosing the parts that made sense to me from various posts. But there was definitely a lot of picking and choosing -- parts that didn't make sense to me, I've simply discarded. So there are certainly versions I don't understand.

I'm planning to take a look back at some articles to indicate places of dissonance, but off the top of my head, I think the point of highest friction is the idea that each stage follows from the last in a systematic way. This story seems to almost work rather than actually working.

OK, looking back a bit, I think the main point of discordance for me is that the 3rd level "masks the absence of meaning". This was repeated often in simulacrum posts. 

I can understand this "masks the absence of meaning" as a thing, but to me it seems more sensible to think of level 3 as "signalling". I like the interpretation where levels 1 and 3 are both "honest in their own way" (level 3 is like "vibing", an honestly expressing what is felt in the moment, just devoid of a concept of truth like that at level 1). This seems incompatible with "masks the absence of meaning".

A "show trial" was given as an example of the mask-absence-of-meaning level 3; this makes some sense, as it hides the absence of rule of law in which statements of guilt would be meaningful (as opposed to simply lying about guilt). But it makes less sense as "honest signalling" to indicate group affiliation with those who prefer rule-of-law-flavored vibes.

Quoting the original wikipedia summary which seems to have sparked much of the discussion:

Simulacra and Simulation delineates the sign-order into four stages:

1 The first stage is a faithful image/copy, where we believe, and it may even be correct, that a sign is a "reflection of a profound reality" (pg 6), this is a good appearance, in what Baudrillard called "the sacramental order".

2 The second stage is perversion of reality, this is where we come to believe the sign to be an unfaithful copy, which "masks and denatures" reality as an "evil appearance—it is of the order of maleficence". Here, signs and images do not faithfully reveal reality to us, but can hint at the existence of an obscure reality which the sign itself is incapable of encapsulating.

3 The third stage masks the absence of a profound reality, where the sign pretends to be a faithful copy, but it is a copy with no original. Signs and images claim to represent something real, but no representation is taking place and arbitrary images are merely suggested as things which they have no relationship to. Baudrillard calls this the "order of sorcery", a regime of semantic algebra where all human meaning is conjured artificially to appear as a reference to the (increasingly) hermetic truth.

4 The fourth stage is pure simulacrum, in which the simulacrum has no relationship to any reality whatsoever. Here, signs merely reflect other signs and any claim to reality on the part of images or signs is only of the order of other such claims. This is a regime of total equivalency, where cultural products need no longer even pretend to be real in a naïve sense, because the experiences of consumers' lives are so predominantly artificial that even claims to reality are expected to be phrased in artificial, "hyperreal" terms. Any naïve pretension to reality as such is perceived as bereft of critical self-awareness, and thus as oversentimental.

For me, I somewhat buy a natural progression between the levels in this model:

• Level 1: truth.
• Level 2: masks the absence of level 1; IE, lying.
• Level 3: masks the absence of even level 2; IE, masks the absence of meaning.

However, level 4 feels less like a natural next step and more like a summary of all the rest of the infinite levels of such a hierarchy -- as if to say "and so on". The implicit claim is that anything worse than level 3 is so bad as to be not worth classifying in further detail.

In my preferred interpretation, we instead think in this way:

• Level 1: truth.
• Level 2: Malign subversion of the level-1 system; IE, lying.
• Level 3: The behavior at level 2 corrupts the meaning of the symbols at level 1 (basically honest people are communicating, but using a language build with liars). What survives is a kind of looser meaning system. Meaning becomes "whatever you can infer"; words therefore have a tendency to say more about group affiliation than about reality.
• Level 4: Malign subversion of the level-3 system.

This leads to some slippage between 3 and 4 for me. If I go with the original description of the levels (in which 3 masks lack of meaning, and 4 indicates collapse of meaning, where symbols refer only to symbols), it seems like signalling should be level 4, not level 3.

I don't know if this is a confusion, per se, but I dislike that there's this undertone in the model that everything above the first level is progressively worse. I mean, sure, it's worse for some purposes, but this quickly fades into the background and becomes a model about what's worse within a particular worldview and for particular purposes.

Complaints that any particular simulacrum level get in the way of truth is not very interesting to someone who doesn't actually care much about truth, and instead is more concerned with, say, social harmony or power. And you might say, well, the posts acknowledge that, but it's done in a way that makes it very clear there are taken-for-granted reasons why truth is the most import thing that won't connect for anyone for whom this isn't true.

When I look at the theory of simulacrum levels I have a reaction like "yeah, that's cool, I get what you're saying, but also you have to communicate at all the levels concurrently all the time anyway, so stop whining about it and get on with living with humans as they are rather than pining for some ideal world that doesn't exist." Not the most charitable reaction, and again not exactly a confusion, but I bring this up because I could see this manifesting as confusion for someone who similarly sees this problem but doesn't quite have the words to put to it.

If I had to guess at why I've grasped the concept but not the level-number mapping, I think the "simulacrum level N" schema makes it harder to learn. There's no intrinsic 2-ness about SL 2 or 4-ness about SL 4, so it's a memorization game. Not a big game, especially if you actually use the concept handles in conversations, but... 

Generally, it's harder to learn a set of vocab words and phrases if there are pairs which look similar. (I think there's some psychology-forgetting theory research on this, but I forgot what it's called) 

Even worse, this pairwise similarity can impede retention in the long-term, in my experience. For example, I am (or at least have been) quite proficient in French, but because my teacher tried to teach all of the days of the week at the same time, they still give me trouble.

EDIT: The way to get around this is by learning each similar concept a week+ apart. I have a special "conflicting concepts" Anki deck when I have to add cards for similar things.

Zvi attempted to address this in a more recent post, but I still feel like there's two slightly different abstractions getting conflated with simulacrum levels that don't quite gel together for me. See my comment on this post:

https://www.lesswrong.com/posts/yqEh9ewKwzig4kzyx/what-is-meant-by-simulcra-levels?commentId=62QE96aqwyLq98mM2

I think that the main thing that confuses me is the nuance of SL4, and I also think that’s the main place where the rationalist communities understanding/use of simulacra levels breaks down on the abstract level.

One of the original posts bringing simulacra to LessWrong explicitly described the effort to disentangle simulacra from Marxist European philosophers. I think that this was entirely successful, and intuitive for the first 3 levels, but I think that the fourth simulacra level is significantly more challenging to disentangle from the ideological theses advanced by said philosophers, and I’m not sure that I’ve seen a non-object level description that doesn’t use highly loaded phrases (symbol, signifier) that come with nuanced and essential connotations from Baudrillard and others. I worry that this leads to the inaccurate analogy of 1:2=3:4, and the loss of a legitimately helpful concept.

I'm confused about the simulacrum level of texts that don't pretend that you should take them literally. 

For example novels, articles in The Onion, ironic remarks, obvious exaggerations, metaphors, or jokes.

Each of these can be used to influence our view of the world, so just giving up and saying that the concept of simulacrum levels does not apply in these cases is unsatisfactory. 

My first understanding of simulacrum levels was that these types of texts would never be level 1 simulacrum because they do not give an accurate map of the real world, and they would typically be at least level 3. On the other hand, level 3 and 4 does not really fit because often such texts do try to influence our view of the world rather than our view of the sender. George Orwell pointed at something in the real world in 1984 and it wasn't important who wrote that novel, so 1984 can be understood as a level 1 text. 

My current understanding (after having only understood simulacrum levels for a day) is that even at level 1, you don't have to understand the text literally. Instead, to find the simulacrum level of a text, you have to first translate the text into a message, and then analyze why the sender wants to send that message. 

I could use more clarity on what is and isn't level three.

Supposedly at level three, saying "There's a lion across the river" means "I’m with the popular kids who are too cool to go across the river." But there's more than one kind of motivation the speaker might have.

A) A felt sense that "There's a lion across the river" would be a good thing to say (based on subconscious desire to affiliate with the cool kids, and having heard the cool kids say this)

B) A conscious calculation that saying this will ingratiate you with the cool kids, based on explicit reasoning about other things the cool kids have said, but motivated by a felt sense that those kids are cool and you want to join them

C) A conscious calculation that saying this will ingratiate you with the cool kids, motivated by a conscious calculation that gaining status among the cool kids will yield tangible benefits.

Are all three of these contained by level three? Or does an element of conscious calculation take us into level four?

(I think C) has a tendency to turn into B) and B) likewise into A), but I don't think it's inevitable)