I mean, significant mental investment sound like typing "sunk cost fallacy" to me.
The whole Urbit system could be described in terms of linked-lists and S-Expressions. Even languages as obscure as K, J or APL have better reasoning than Urbit.
Obscurity only leads to smaller number of people wanting to explore something. Only people who stays with it are "believers" and not experts.
It's not worth it to me, I'd rather do other things and this is almost absurd levels of exclusion but I like the obscurity-as-a-quality-control method approach in general for some projects.