As with many other subreddits, /r/LegalAdviceUK (which had been dark since the start of the blackout) has been sent a thinly-veiled threat by Reddit.
So they’ve reopened in order to start moving the entire community of 810,000 subscribers to somewhere else.
As you can imagine there are a number of legal professionals who moderate that sub, and they really don’t take kindly to being threatened. They sign off their reopening message with “Fuck /u/Spez and long live John Oliver.” but for the real fun you might want to look up a very famous British legal case they reference, Arkell v Pressdram 1971.
There are moderation assistant bots and a number of settings that can be used to ease moderation. Because of the free API, big servers can make custom bots to suit their needs.
Moderating anything with over 10k active members is going to be a lot of work, no matter how streamlined the tools are. People are very creative at finding new ways to be assholes.