The metadata shows the document written by Kim Brooks, because she herself stated that she removed the e-mail address and copied the text into a document to make it shareable as a PDF. So this in itself does not prove that the statement is genuine.
Exactly. If the claim was that the PDF itself had been created 10+ years ago and passed on as original, then the metadata would be relevant. As it is it's simply a container that people use to send things in.
If I were asked to look at it in a more forensic manner, I'd look for things like the font face and the anti-aliasing used as a way of dating it, as those have changed over the years. If it were a newer system font rendered on a higher res display then that would scream "faked" but both look like you'd expect for the time, so if it were a fake then someone has thought of absolutely everything, which people tend not to, or someone faked it and then waited 14 years to release it? That doesn't seem realistic.
The other thing I'd try to do is find the chat system involved and whether it formatted nested discussions in that way. This may be difficult but doable, especially if someone knows what system it may have been.