And there is almost certainly a decompression you can run on some of the information to fit whatever sort of pattern you're looking for.

I've explained before why this reasoning is misguided: to get arbitrary desired information processing out of random processes, you have to apply an ever-expanding interpretation, meaning that any model that calls e.g. a rock a computer is strictly longer than a model that doesn't because the former would have to include all of the latter, plus random data.

So a rock is not a general use computer (though it can be used to compute a result, if the computation you want to perform happens to be isomorphic to whatever e.g. heat transfer is going on right now).

Now, with that in mind, I was among those who claimed that rocks are agents as defined by AnnaSalamon et. al, so how do I reconcile this with the claim that rocks aren't computers?

Well, it's like this: An agent, as defined here, has internal dynamics that could, in principle, be understood as a network of counterfactuals and preferences. A computer, OTOH, does in fact do the work of altering your beliefs about an arbitrary computation. (Generally, that just means concentrating your probability distribution onto the right answer, when before you just figured it was within some range.)

And since Eliezer_Yudkowsky claims that even a pebble embodies the laws of physics, which are nothing but a causal network containing counterfactuals and a species of preference (like energy minimization), that means the term "agent" is carving out a much huger chunk of conceptspace than I think AnnaSalamon et al intended. Which is what makes it hard for me to understand what the agent concept is supposed to be distinguished from.