I’ll follow your lead in elaborating the argument further, but renumber for clarity:
1.(unexpanded) My meta seemings (about seemings) are reliable indicators of truths about seemings
2.(observation) My moral seemings seem (to me) reliable indicators of moral truth
3 (combine 1&2) My moral seemings are reliable indicators of moral truth.
4.(observation) It seems to me that harming innocents is wrong
5.(combine 3&4) I know that harming innocents is wrong
6.(unexpanded) If I know something, that something is true.
7.(combine 5&6) Harming innocents is wrong.

My basic claim here is that all of the unexpanded and observation claims (1,2,4,6) are reasonably thought of as “is” claims.

But perhaps you are proposing that this is how an ethical intuitionist would defend the moral principle that harming innocents is wrong. There is a simple reason why no intuitionist should present this as a derivation of the moral principle: the form of the argument is invalid (and hence {1,2} is not a set of descriptive propositions that entail a normative proposition).

Some ethical intuitionists explain how it is that we know moral truth in terms similar to this (but the second premiss would be that seemings are reliable, not that seemings seem to be reliable). Taken like that, it is missing an intermediate conclusion ‘2b. therefore I know that harming innocents is wrong’. The step from 2b to 3 is valid but the argument as a whole is still invalid. Furthermore, such externalist explanations of knowledge are explanations of how we know what is true, when it is true, so properly formulated it would take 3 as a premiss, and 2b would be the conclusion.

Moreover, such explanations of moral knowledge don’t entail that belief in the conclusion (3) is not a basic belief, (in the sense that basic beliefs are where the regress of justification stops). For example, if intuitionists were then to explain the seeming and the reliability in terms of conceptual competence and the nature of the concepts involved their whole story could be that ‘harming innocents is wrong’ is a self evident proposition.

Finally, you might say, great, the step from 2b to 3 shows that you can derive an ‘ought’ from an ‘is’, since 2b is prima facie a descriptive proposition whilst 3 is normative. First of all, that’s fine, since I was not trying to defend Hume’s critique but point out that it was about entailment of normative propositions rather than knowledge of them. Secondly, however, since knowledge is factive it is less clear that it is a mere quibble to point out that the proposition ‘I know that harming innocents is wrong’ contains a normative notion. The normative notion is within the scope of a factive operator and that looks like a ground for saying it is a normative proposition. Thirdly, setting that aside, 2b is still the wrong kind of proposition to embarrass Hume’s critique. He is criticising people for deriving things like ‘you ought to help Fred’ from ‘Fred is suffering’ alone. That you can derive ‘you ought to help Fred’ from ‘I know you ought to help Fred’ is beside his point.

The issue of knowledge you raise is that of knowing the general ethical principles from which we derive particular ethical conclusions, such as when I infer I ought not hit Johhny because harming innocents is wrong, hitting is a harm, and Johhny is innocent. Whether I know that harming innocents is wrong may well depend on the truth about the nature of ethical intuition. If I don’t know the ethical premiss then I don’t know the conclusion despite the validity of the inference. Perhaps it is only if ethical intuition is reliable that I know the ethical premiss. But the issue over deriving ‘ought’ from ‘is’ is about whether the inference is valid.

The validity depends on the nature of the relation of logical consequence. The denial of deriving an ‘ought’ from an ‘is’ is the claim that there are no sets of purely descriptive propositions that entail a normative proposition, alternatively, that any set of propositions that entails a normative proposition contains a normative proposition. Quite clearly, the fact you mention, that whether I know an ethical principle depends on a descriptive truth about the reliability of ethical intution, has nothing to do with whether there are any sets of purely descriptive propositions that entail a normative proposition. Hence that fact is irrelevant to the question of whether we can derive an ‘ought’ from an ‘is’.

If I can even conceive of that intuition being wrong, it’s either because I have a conflicting intuition, or because the relevance of the intuition is based on false premises. In the case of conflicting intuitions, my intuition not to torture is weighed against the fact that, if I don’t, a thousand people might die in a terrorist attack, and my intuition against torture might be wrong as a guide to action in this case, but not generally. In the case of the false premises, maybe it turns out that the victim of torture is not really a person, but a non-sentient automaton, and if I examine my intuitions, I discover that I’m really only against the torture of sentient beings. Yes, there are tons of “is-es” there, but it ultimately comes to an “ought” (or two).

An argument for an “ought” is typically built on some set of more basic “obvious” claims that the speaker assumes their audience will accept without argument. Many of those claims have their own supporting arguments somewhere else, but those arguments are also be built on further obvious claims.

Eventually we end up with with a set of basic supporting claims that seem obvious, but which don’t have much in the way of explicit arguments supporting them. Yes, almost always one of these obvious but not explicitly argued claims is of the “ought” type. So in this sense every “ought” is derived from an “is.”

Did you mean to write something else? What this actually says is that every “ought” is derived from an “ought”.

I’m instead pointing out that most every attempt to derive an “ought” is based ultimately on “is” claims about the reliability of our intuitions about such more basic “ought” claims. If we can’t find a coherent way to integrate these “is” claims with the rest of our network of reasonable “is” claims, then we can’t argue coherently for such “ought” claims at all.

And this says it again. I think the logical closure over what you said is this:

Every “ought” claim
1. is ungrounded and ultimately meaningless, because every ought claim depends on another ought claim (you argue this twice, but it fails to play any part in the main point you are making), and
2. “comes from” “is” claims, because you need to have facts to make an argument.

You have no evidence for the first claim; and the second is irrelevant. Yes, “ought” claims make use of an infrastructure of “is” claims; but that isn’t what people mean when they say “ought doesn’t come from is”. They mean that an “ought” claim can’t bottom out entirely in “is” claims. And not only did you not argue with that, you agreed with it.

Now, does that make wikipedia worthless, no; accepting it as straight fact, however, is obviously a bad idea.

Maybe, but by what standard of discernment can, or do, you make that claim?
Does this suggest there is an is? From which we derive ought?

To what extent is Wikipedia and assault on ‘Authority’ or esp the tenure that goes with it, which is spent of lifestyles that cranks up ‘relative deprivation’ in those who have not secured tenure? Do education systems tend to select with a far too broad an apparatus? There will be may losers, but the winners will be of superior quality, and the ‘losers’ afterall, have transferable skills – or appetites of entitlement.

Now, does that make wikipedia worthless, no; accepting it as straight fact, however, is obviously a bad idea.