This doesn't seem like a sophisticated enough treatment to help with understanding.

(1) Fiction and nonfiction are not inverses of each other in any reasonable sense of the word "inverse". Regardless of whether it's fiction or nonfiction, we have no choice but to use our mental models to understand the content, and that mental model involves simplification.

(2) The reason that "Superman is from Krypton" is an objective statement is the same reason that the name of New York City is objectively New York City: we have a robust way of determining certain social agreements, like what something is called. The agreement itself is a form of intersubjectivity, but given the agreement (which covers method, not content), the objective facts are not. In the case of a city, it's historical precedent backed up by the assent of the governing body (e.g. Mayor's office). Facts that would require empirical evidence to be objective nonfiction are instead determined by the empirical evidence of what-the-creator-says (still bounded by things like logical consistency). The point is that there is no difference in whether there needs to be evidence, only in what the nature of that evidence needs to be depending on whether we are talking about fictional or nonfictional matters.

(3) That we can pay attention to some things and not others has nothing to do with objectivity or subjectivity per se. If we map the moon's surface in higher detail than we map Enceladus' surface, both planets still objectively have the surface they have, we just know that objective reality to different levels of accuracy. Indeed, if you can impinge upon the truth value of an objective statement by striving for a goal, you don't have an objective statement to begin with.

(4) Whether or not we have any agenda when referring to an objective fact is also immaterial to whether the fact has or does not have the status of objectivity. Again, if your agenda can sway the truth value of an objective statement, it isn't an objective statement. The notion of "objective" models the situation where there is something whose qualities are not dependent on how you think about it. Tossing that in the rubbish bin and instead letting in all sorts of goal-based influences is a wretchedly poor model for understanding a universe which is chock-full of things with qualities that are not affected one whit by your goals.

(5) The discussion of the intersubjectivity vs. objectivity of the blue sky is confusing epistemology and ontology (and semiotics).

I do not see how someone could read this article and come up with a deeper and more precise, rather than a more confused, view on the nature of objectivity, subjectivity, and intersubjectivity, and the weird cases that seem to fall somewhere in between (many of which have to do with us using declarative definitions to communicate with each other, but exemplar-based definitions in our own cognition).