I tried emailing two of the names listed at the time, for two different purposes. I got a little bit of a response from one, nothing from the other.
I read the "rules" for W3C groups and in order to actually participate you need to be a member of a big organization and all this other stuff. I'm not sure anyone would have listened.
Almost all W3C groups nowadays do almost all their work in public on public mailing lists; actually being a member of the WG is rarely a requirement for participation.
And if it was sent between the spec becoming a Candidate Recommendation and going to Proposed Recommendation, it must (in theory) have been addressed. If not, something's gone wrong process-wise with how the group was operating (and from poking around a bit, it seems likely it did). Le sigh. :\
Thank you for the explanation. This has been my only experience with the W3C system and as an outsider it was very intimidating. I'm certainly willing to accept the idea that I wasn't going about things the right way or understanding what I was reading!
Many of the smaller, newer groups with fewer people with a background in the W3C end up being somewhat dysfunctional and with odd processes and that almost certainly makes it feel harder to participate than it should be.
From prodding around a bit (notably [0], which sadly is in Member-only space, but plenty of administrivia is there, and in principle no technical work for almost all groups), it seems like every issue reported to the Working Group (regardless of where) should have ended up with a GitHub issue, with [1] being meant to have been all issues while the specs were in CR.
Pointing in the specs to a mailing list to report issues, and then relying on someone to copy them into GitHub, seems doomed to fail: it's far, far too easy for one thing to not get copied. Really the "Status of the Document" should've pointed to GitHub for new issues being filed (possibly with a fallback to the mailing list for those unable to use GitHub for organisational or other reasons).
I read the "rules" for W3C groups and in order to actually participate you need to be a member of a big organization and all this other stuff. I'm not sure anyone would have listened.