I think that this is both an incorrect and amoral way of thinking about externalities. Externality costs Must be real incurred costs, not just hypothetical opportunity costs. Otherwise they are useless for economic analysis and lead to repugnant conclusions

IF you drop trash on your neighbor's lawn, that is an externality. If you refuse to mow their lawn, that is not an externality, no matter how much they have to pay someone else.

Efficiency is not an inherent good, and Pigouvian taxes on inefficiency are a huge moral hazard. Is it inefficient for a doctor to play with their children instead of work? Who are the decision makers?

The comments here have been very focused on the case of implementing some system like this for housing (which to be fair was the example the book used), but as I said in the original comment, I actually don't think this is a workable or desirable system for property taxes on owner-occupied housing for roughly the reasons that you dislike it. Someone's home is not just some financial asset and economic efficiency is not the only important consideration in society.

I brought it up specifically in this context (and article about patent litigation) because I think it is potentially a good idea in some domains (like patent law) where the overriding consideration should legitimately be economic efficiency. I think it is entirely reasonable to design our intellectual property rights around the idea that the person or firm that can derive the most economic value from any piece of IP is the most desirable owner of that IP.

That's fair. I agree that intellectual property does not have the same foundational justifications as physical property. IP justifications ARE generally based on economic efficiency rationales, and typically cut contrary to physical property rights (e.g. Why cant I produce a copy for sale with material I own, in a factory I own)

I was mostly picking at how you invoked externalities, which is a major pet peeve of mine. I feel that between sloppy economics and utilitarianism, the concept of externalities is invoked anytime anyone doesnt get what they want.