Well, they could just say: “We made a script to track every mod who closed their sub, revogate its mod permissions and notify all other mods in the sub with an automatic message”, which basically frees them from any charges regarding community content.

They could, however, be sued for not actively removing illegal content, such as pirated things and MAP related things (e.g. r/jailbait)

Isn’t Reddit GDPR copliant? Because if they are, they can’t simply undelete things without users’ permission