Kolmogorov complexity suggests a Tegmark IV mathematical universe where there are many more simulations than there are base realities.

You are supposed to be counting observers, not realities. Simulations are more common, but also smaller.

Do you ever worry that by modeling others' minds and preferences you give them more local significance (existence) when this might not be justifiable? E.g. if Romeo suddenly started freaking out about the Friendliness problem, shifting implicit attention to humanity as a whole whereas previously it'd just been part of the backdrop, and ruining the traditional artistic merit of the play. That wouldn't be very dharmic.

Kolmogorov complexity suggests a Tegmark IV mathematical universe where there are many more simulations than there are base realities.

In a Tegmark IV universe, there's no meaningful distinction between a simulation and a base reality -- as anything "computed" by the simulation, is already in existence without the need for a simulation.

I think that when people ask if we are in the base reality versus a simulation they are asking the wrong question.

If that's what they happen to want to know then it's the right question. That is to say it is coherent question that corresponds to a pattern that can be identified within Tegmark IV that distinguishes that location from other locations within Tegmark IV and so can potentially lead to different expactations.