You’re exaggerating of course, but I don’t think it’s terrible at all; the opposite really. It’s likely incredibly useful for creating LLMs with specific knowledge or behavior.
The categorization into subreddits alone opens up so many possible applications. Imagine for example training a conversational AI with data from specific subreddits like science, askscience, biology, physics, astronomy,… or posts by users that frequent such subreddits in order to create sort of an academic AI.
You could do the same for all sorts of topics: Want a sports commentator AI, use sports related subreddits; an AI that supports you in writing a novel, use creative writing subreddits etc. Don’t want your AI to spew political opinions, exclude political subreddits from your data; don’t want it to use offensive language, only use well-moderated subreddits etc.
I like the comment guidelines from Hacker News. E.g.