By contrast, when I'm trying to assess my own future actions, I don't see what need concern me except whether act A or act B bring about more good.

You are a consequentialist. Your reply is precisely accurate, complete, and well-reasoned from a consequentialist perspective, but misses the essential difference between consequentialism and deontology.

Edit: Quoting the OP:

If a deontologist says "lying is wrong", and you mentally add something that sounds like "because my utility function has a term in it for the people around believing accurate things. Lying tends to decrease the extent to which they do so, but if I knew that somebody would believe the opposite of whatever I said, then to maximize the extent to which they believed true things, I would have to lie to them. And I would also have to lie if some other, greater term in my utility function were at stake and I could only salvage it with a lie. But in practice the best I can do is to maximize my expected utility, and as a matter of fact I will never be as sure that lying is right as I'd need to be for it to be a good bet."... you, my friend, have missed the point.