I've noticed some Harmony shippers use this quote to support their pairing: 'At once, Hermione Granger's voice seemed to fill his head...', however the 'shrill and panicky' part is omitted. Why?

In probably every shipping fandom, there are some प्रशंसकों who are very selective in what they use to back up their ships. They ignore parts which contradict. It's probably even और true for fanon ships, because they have to खोजिए harder for their supporting material. In this case, they're trying to use the fact that Harry thought of Hermione to prove he's focused on her, and ignoring "shrill and panicky" because that isn't complimentary.

I would like to point out that because of Ron's issue with Harry's supposed enter in the tournament, Harry has been hanging out with Hermione. But he missed Ron terribly because hanging out with Hermione are trips to the पुस्तकालय and less fun, less humor. "She just wasn't Ron."
I hardly see people shipping Ron and Harry, btw.