I always enjoy it when people go to absurd lengths to try and defend their position. I had another conversation elsewhere where someone seemed to think that asking how Rowling could have worked Dumbledore wearing leather chaps into the story as a signifier of his sexuality.
It is Rowling's responsibility to find a way to work it in to the story (I don't see anything wrong with Dumbledore being a bit more specific during his conversation with Harry in Deathly Hallows for example). After all, if Rowling hadn't been asked this question at this time we might never have known about Dumbledore. After all, we're not all slash writers, it's not our job to assume that all the boys are sleeping together and all the girls are sneaking off to orgies in the Ravenclaw Tower
...and I enjoy going to absurd lengths for a cheap laugh. What a match!
I guess the point I am reaching for is this: she shouldn't HAVE to work that detail into the story. Not every detail is crucial, and you would need a compelling reason to tell readers that particular detail. She had to decide what was important to tell IN THE BOOK, and what wasn't; the fact that she had that in mind is interesting, but not crucial.
Dumbledore's alleged orientation doesn't matter enough to the story to be worth spelling out to the reader. Nothing in the story requires him to be a particular orientation, and trying to shoehorn that into the narrative would either be an exercise in awkwardness or offensiveness. No matter how casually she presented it, there would be readers with extreme opinions on the topic who would be distracted from the main point she wanted to make (about Love being the most powerful magic).
Making a character gay in our society is a huge investment. It means that you have to develop that idea; if you plant the notion, you're going to provoke your readers to come up with ridiculous and offensive assumptions about what it means to be gay (like the ones I made, and the leather chaps comment). You have to worry about two prongs of reaction: the anti-gays who will be mad that the character is gay at all, and the pro-gays who won't be satisfied with any perceived mischaracterization of the lifestyle. Frankly, I'm glad she didn't try to deal with it, because I don't think she would have handled it well under any circumstances. Maybe a better writer could, but looking at how she handled the scenes of young teenage love, I'm relieved she didn't try to tackle homosexuality.
For me, it comes down to this: I read the books. I hear this interview where the author says "DIG"... I reconsider the books with that detail thrown in, and ask myself, does it change anything? No; D is still a good, noble, and flawed character. Is it sad that more people on our planet can't recognize that and stop worrying so much about whether someone is gay? Yes.
Now, I'm sure I've left holes in my argument... but someone just started crying downstairs, so no time to edit further. Be merciful!