Thank you so much Stefan. I just read (and voted for) your essay, and I love how you're also discussing macrostates. I particularly like your analogy of how entropy (or irreversibility) arises only at the macroscale, and saying that this is analogous to how goals arise solely at the macroscale. In my view, the corollary analogy would be in terms of error-correction: only error-correction for causal relationships can occur at the macroscale.
You bringing rigidity into this in your essay is an interesting avenue - I didn't explore what multiple-realizability means for the physical properties (only the causal/informational ones). It makes me think it's worth investigating whether there are certain physical requirements (necessities) for causal emergence to occur.
All the best!
Erik P Hoel