I haven't considered the situation you bring up. I am for the singular they when it is being used to describe and indeterminate person. Are you suggesting we use singular they for a particular person until we get explicit confirmation about their pronoun preference?
I wonder if you weren't downvoted for using the subjunctive mood in your comment ("if that were the intention here") which seems to imply that you believe it was not the intention and was instead a "mistake".
Also, I've seen several comments here of someone making what I presume are honest mistakes in using the wrong pronoun and being publicly shamed for it.
It doesn't to me. Maybe it varies by region.
For example, what would you refer to me as? "Nadya wrote on her blog" or "Nadya wrote on his blog"? (hint: You'd need to dig rather deep into my post history to find the "proper" one.)
@ruraljuror's example
Further context removes that ambiguity. Although you could rephrase it as "Julia wrote on their own blog" or even remove the pronoun altogether: "Julia wrote on Julia's blog" (which is only ambiguous if there is another Julia).
And Nadya is hard—I would go for gender neutral on that one. :-) (It's not that I dislike singular ‘they’, but sometimes it can make sentences awkward.)