I’ve seen plenty of communities where it’s clear that the mods only stop by from time to time and they get by just fine, spam and malicious posts will still be a small minority. Some set automod on a shoot first, ask questions later setting where all reported comments get deleted until the mod restores them.
I really don’t think finding new moderation will be an issue. As much as it would be nice for Reddit to be screwed over by the mods it’s going to be a non-issue for them, there’s already measures in place to prevent subreddit parking and plenty of willing volunteers.
In the process of taking off at best. That’s nothing compared to Twitter right now.