when we use moral terms, we may be referring to a shared concept of "normativity"... This may well not be the case, but it is a possibility that I'm not willing to rule out...

Agreed.

I disagree with your approach of assuming linguistic reductionism.

Well, but I don't 'assume linguistic reductionism'. What I say is that if the intended meaning of 'ought' refers to structures in math and physics, then linguistic reductionism about normative language is correct, and if it doesn't, then normative language (using its intended meaning) fails to refer (assuming ontological reductionism is true).

But when people argue over realism vs anti-realism, they are not arguing over whether people sometimes stipulate different definitions for "morality", but instead are disagreeing over the nature of the intended meaning of 'morality'.

Philosophers usually are, but not always. One thing I'm trying to avoid here is the 'sneaking in connotations' business performed by, in my example, Bill Craig.

I don't think you've succeeded in dissolving the question that people are really asking.

No, I haven't, and I've tried to be clear about that. But perhaps I need to edit 'Pluralistic Moral Reductionism' with additional clarifications, if it still sounds like I think I've dissolved the question that people are really asking. What I've dissolved is some debates that I see some people engaged in.

Edit: Also, I should add that I'm fairly skeptical of the idea that humans share a concept of morality or normativity. I do intend to write something up on the psychology and neuroscience of mental representations and 'intuitive concepts' to explain why, but I've got several other projects stacked up with priority over that.