www.lesswrong.com/posts/qfitpqvQzeZy2mSGi/the-fourth-world

This sentence compresses viruses too far and becomes inaccurate in two ways.

First, a virus is not just “a ... molecule.” Standard references describe viruses as infectious agents composed of a nucleic-acid genome packaged within a protein shell (and some also have a lipid envelope). That makes a virus particle a structured assembly of multiple components, not simply a single molecule.

Second, viruses are not self-replicating on their own. They are obligate intracellular parasites that must enter living host cells and use the host's energy, ribosomes, and other machinery to make new virus particles. As one virology text puts it, viruses "do not increase in number by cell division; instead they assemble from newly synthesized protein and nucleic acid parts."

So while the post is using viruses as a rhetorical analogy, calling a virus "a simple self-replicating molecule" is factually misleading: viruses are noncellular infectious agents made of genomes plus protein coats, and they replicate only by exploiting host cells.