It could just be karma whores expanding to other platforms than reddit. Idk if it's still a thing but there was a time on reddit where people would steal posts, repost old top posts and aquire as much karma as they can on new accounts. Then sell the username to shills so they can push their agenda without looking like an obviously belligerent shill. They might try the same approach on lemmy before realizing karma doesn't mean shit here which is where you see them deleting their accounts.

While possible I do think it's a stretch, I also think it would be completely inefficient to try and train any LLM by feeding it data from lemmy. I wanna say the average number of active users on lemmy at any point is around 40,000. Compared to what google says reddit's avg daily active users which is 52,200,000 users per day, it would seem like a complete waste of resources.