I think there are many important unsolved problems in the theoretical/philosophical parts of rationality, and this post seems to under-emphasize them.

Agreed to an extent, but most folk aren't out to become Friendliness philosophers. One branch that went unmentioned in the post and would be useful for both philosophers and pragmatists includes the ability to construct (largely cross-domain / overarching) ontologies out of experience and abstract knowledge, the ability to maintain such ontologies (propagating beliefs across domains, noticing implications of belief structures and patterns, noticing incoherence), and the disposition of staying non-attached to familiar ontologies (e.g. naturalism/reductionism) and non-averse to unfamiliar/enemy ontologies (e.g. spiritualism/phenomenology). This is largely what distinguishes exemplary rationalists from merely good rationalists, and it's barely talked about at all on Less Wrong.