How about the fact that beliefs about physics actually pay rent? Do moral ones?

Not in the sense of anticipated experience, however they do inform our actions.

How about the fact that beliefs about physics actually pay rent? Do moral ones?

Good point. And no, they don't - unless you need rent to tell you about people's preferences.

But science isn't about words like "exist", "true", or "false". Science is about words like "Frozen water is less dense than liquid water".

Only because the force of the word "exists" is implicit in the indicative mood of the word "is".

Come on people. Argument by analogy doesn't prove anything even when the analogies are valid! Stop it.

But they can help explain what people mean, and they can show argument prove too much.

• The flowchart in the original post has many endpoints about what morality might mean.

I could draw an equally complicate flow chart about what "truth" and "exists"/"is" might mean.

• There seems to be no universal consensus on what specific actions are moral and which ones are not.

The amount of consensus is roughly the same as the amount of consensus there was before the development of science about which statements are true and which aren't.

• People have strong opinions about morality despite the fact that statements about morality are not subject to empirical validation.

People had strong opinions about truth before the concept of empirical validation was developed.

You can't point at anything for claims about pure maths either. That something is not empirical does not automatically invalidate it.

Morality is not just social signalling, because it makes sense to say some social signals ("I am higher status than you because I have more slaves") are morally wrong.

But science isn't about words like "exist", "true", or "false". Science is about words like "Frozen water is less dense than liquid water".

True.