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?

Her voice's tendency to become shrill is not evidence that Harry dislikes her as a person or that the ship is unsound. That part of the quote is probably omitted because it's irrelevant to the point they're trying to make. Hermione's voice naturally becomes madami shrill when she's scared or overly excited; it's all throughout the books and if you asked Ron about it he'd agree so I don't see why you're so hung up about this.

The point Harmonians are trying to make with it is that when he had the disturbing dream/vision about Voldemort the first person he thought of going to for help wasn't Ron, Lupin, or Sirius - It was Hermione. She's first on his list, his go-to girl, when he has a problem and needs someone to talk to.

Well cuz we´re shippers and we try not to look to details that can make out ship look less real. That´s my personal opinion