Couldn't really tell you. I haven't done any moderation in many years. And have no knowledge of how their DB system or backups are structured. But make no mistake, Reddit has admin rights and the ability to takeover any sub if they don't feel the mods are doing a good job, and there's been precedence for such action, either due to mod abusing and shuttering a sub, or just not engaging at all or even just going afk and abandoning a sub.

I dont think Mods can outright delete comments or submissions, only hide them. Only a user can overwrite and delete their comments. So....unless basically all users started scrubbing comments it would be hard i would guess. And i wouldnt be shocked if they had replicas or DB backups crawled at the page/submission level to roll back off of to protect such an act. Heck Pushshift was doing about that. I really detested that guy for how he handled privacy. Even had people sign up to exemptions and just straight ignored specific requests to have their user pages excluded from crawling.