I have this same problem now (October 29, 2023), which, if I recall correctly, did not happen before (don't remember when was the last time I tried to turn a community comment page into pdf, sorry).
I don't believe it is a problem with my computer settings since it has been static for a long time (still running Mojave 10.14.6 because certain apps must now be "rented"). My guess is that something got changed in the way the web pages are defined here because everything in the page is included in the pdf and only the text responses of the various correspondents are dropped (if the response includes an image, the image does get included in the pdf). This happens in both Firefox (115.0.3) and Safari (14.1.2). Needless to say, this does not happen elsewhere so the problem is a discussions.apple.com issue.
Since the OP is using Mac OS 13.3 (and I am using 10.14.6), it is likely that some "new standard" prevents older browsers from including the text of responses in the generated pdf. It is known that printing of web pages is essentially left up to the web designer. Hence, it is likely that a change was made in the latest revision of the code that is used to generate the community pages (everything changes, I suppose). If so, the only hope for a solution to this problem is to have the code revised to solve this issue. How one reports this to Apple is, I guess, up to the gods. :-)
BTW, yes, one can select the text and put it into a text document (or any word processor) but if the comment includes images, well, I guess it might get complicated.