After talking to a few people I PM'ed, it appears that Reddit itself is shadow-deleting the PMs automatically, not just a setting on the auto-moderator (which is utterly baffling the subreddit's staff, apparently).

Just like shadow-banning users, this underhanded censorship from Reddit itself is quite disgusting. Then again, after the recent debacle of a certain administrator being hired then fired and the fallout from Reddit's owners trying to cover it up, such despicable practices on their end really shouldn't surprise me.

Anyway, my digression aside, I've written the PM out in a Google Doc, which can be accessed below.

https://docs.google.com/document/d/1Ejn8v2LBUOujA4040NIN38a2-EQrUgk2ZTS-Ftflidk/edit?usp=sharing

I hope this helps ya'll make a couple of quid!