Is it simply a matter of personal preference, cultural norms, or social contracts?

So is god (or at least I’m sure you’d agree, the vast majority of gods), so not sure why appealing to a higher power solves this.

If you rely solely on human reason, empathy, and self-interest, you will struggle to establish a consistent moral framework for setting boundaries.

The framework is what’s healthy for you and others. Knowing your personal limits and goals. There isn’t some supernatural “boundary dimension” you need to tap into or anything.