Dropsitenews published a list of websites Facebook uses to train its AI on. Multiple Lemmy instances are on the list as noticed by user BlueAEther
Hexbear is on there too. Also Facebook is very interested in people uploading their massive dongs to lemmynsfw.
Full article here.
Link to the full leaked list download: Meta leaked list pdf
It’s no different from posting on usenet back in the day. You have to assume it’s all completely public. People are gonna train their AIs on large public text repositories whether they’re given permission to or not.