I don’t have any problem with JK Rowling shipping her own characters. Fandom is its own thing.
I think representation does matter, especially to kids, but it’s not about checking boxes, and in fact I feel quite strongly that that approach is counterproductive. As a fagling, I never had a problem identifying with characters because they were (implicitly) straight. Overwhelmingly, my beef was with the presence of negative representation, not the absence of positive representation.
The way to show kids that it’s OK to be gay is to not tell them it isn’t.. The way to show kids that it’s “normal” to be gay is… well, don’t do that, because it’s not true. If you are queer, your romantic life will not work the same as a straight person’s. It irks me that writers pat themselves on the back for “representing gay characters” when they’ve actually just slapped a false label on a character who - precisely because they are positioned as “normal” - corresponds to a straight person in real life.
So, good for JK Rowling for not writing a check she has no intention of cashing.