From W3C Wiki

W3C hosts hundreds of mailing lists with hypertext archives. (@@note search engine too)

The public-html list, like most large mailing list, includes meta-discussion such as...

We haven't discussed top-posting yet (Apr 2007), but surely it's only a matter of time.

Mailing lists are, of course, a great source of semi-formally recorded knowledge... see EmailVocabulary and, for example iCalendar todos from email archives

hmm... PPR:ListMode Mail Archives Mail Archives

Google Groups -- hosting mailing lists since when?