Yeah, they claim that as of 2022 they had trillions of messages in their database, and this website claims four billion messages are sent per day as of 2022, apparently according to Discord, although I wasn’t able to verify that source.

No, it’s definitely still valuable. It’s one of the biggest repositories of human-to-human communication on the web. I’m sure it will be even more valuable moving forward because you don’t want to train LLM models on LLM-generated stuff, and there isn’t as much incentive on a platform like Discord for bots to masquerade as users… unlike on a persistent public and searchable forum like Reddit, where there are obvious incentives to fabricate posts and comments to sell stuff/astroturf/spin public opinion. Bots exist, of course, but they’re identifiable and can be excluded.