Risk management through diversification is a totally different use of the word diversification

Totally different than what?

1 is not something people actively "think" about

Sure they do, but to make it more stark let me change it a bit: "Am I pretty?"

More generally, this example represents the whole class of subjective opinions.

If you feel 2 doesn't have a correct answer, then it seems you're endorsing some form of moral nihilism

Not quite, just rejecting moral realism is quite sufficient here. But in any case, people do think about it, in different ways, and I don't know how would one determine what is a "correct" answer.

This example represents the distinction between descriptive and normative.

For 3, people are not actually looking for the "best" answer; they want a satisfactory answer.

Also, not quite. People do want the best answer, it's just that they are often satisfied with a good-enough answer. However the question of what is "best" is a hard one and in many cases there is no single correct answer -- the optimality is conditional on certain parameters.

This example represents the individuality of many "correct" answers -- what is correct depends on the person.