Earlier quoted context omitted.
> "Thing" is only considered correct because the culture has decided it is correct. If it changes to the alternative you proposed, then that would be correct. Sure, but it's not correct now, despite being cultural.
Exactly. The culture is what determines good spelling.
Again, it's cultural, but that doesn't make it subjective. The fact that it will be different in the future doesn't tell you that it's already different now. There is a fact of the matter here on which everyone already agrees; it's as objective as any other fact.