The biggest problem I see right now is with deleted and removed content.
Generally there is a reason for why someone would want to delete/remove something on Reddit.
If someone posts something that should be removed (spam, illegal content, hateful content), it shouldn’t stay mirrored here. If someone deletes a post/comment on Reddit (they’re getting harassed, they accidentally shared personal info, stalkers), it shouldn’t stay mirrored here.
A chunk of my moderation experience is from a university subreddit where stuff like that DOES happen, putting a real person at risk.
I like this idea and want it to succeed, and this is a concern for me. I don’t know about the legality/liability, but I think even Google updates their caches when stuff is deleted and tools like ceddit/removeddit/reveddit don’t let you see stuff that’s deleted by the user.