This comes pretty darn close to what the author is asking!
> Right now every channel is meant to be both transient and permanent. I know that’ll never change, so create a new “Lore” or “Archive” channel where the moderators tap on wisdom and preserve-forever statements or threads, and they get added over there. Think of it as “Pinning” but they’re pinned forever and there’s a bunch of them.
Disc.wiki seems to literally provide a similar feature, check!
> Make it possible to export this Lore/Archive channel to a reasonable file, like JSON or any other text format.
Disc.wiki provides a web interface for browsing "pinned" messages. HTML is a mostly parse-able text format, so check!
> At the very least, consider some sort of “FAQ” feature/contingency that does a similar function to the old-style FAQs, so people can contribute sets of knowledge in a structured manual instead of an endless search for terms from everyone who ever touched a server.
Ok, there's still some room for improvement. Disc.wiki's homepage claims their docs[0] are built on disc.wiki, so something similar could work.
There could be an open source version of both the cms and the bot but that's at least a step in the right direction.
[0]: https://disc.wiki/docs