That’s fair.

It’s one of the biggest repositories of human-to-human communication on the web.

I am showing my age and have spent decades on various web forums. These sites have thousands, or even tens of thousands, of users and huge quantities of threads some of which can be very deep. Yes, each individual site isn’t that big but there are tons of these things scattered around the web and I’m sure they’ve been crawled. One of the many, many, many manymanymany Ford Mustang forums has > 2 million replies. thirdgen.org, an 80s-early 90s Camaro/Firebird, forum has 763,427 threads with 6.45 million replies going back easily 20 years, which is well before bots.

Discord does have 154M monthly users, so you’re probably right that there is more content there than across all the various boards. It’s also probably a heck of a lot easier to crawl than a bunch of different web forums.