What led you to believe I'm interested in piracy? Double check your assumptions. I'm interested in rational moderation and intellectual property laws.
The law is pretty much settled on this, there is no real danger of some surprise lawsuit; that's not how the copyright system has worked for decades, now. They'll get a notice first, for a specific instance of copyright infringement, and they'll take it down. If that really is their concern (and I do not believe it is really their concern) then it's unfounded and they can unblock these communities as they suggest they will do in the post.
And to be clear, there was no given example of these communities not adhering to their own rule of not linking to infringing material. So the "omg it's cached here" argument is weak even if copyright holder behaved as you are imagining, which they do not.
No big government or corporation is likely to come after an American hosted site for weed, or cars, because those things are socially and legally accessible in that country, but pirated media isn't.
I don't know what this means. Do you mind elaborating or rephrasing?
What are your thoughts on capitalism in your utopian society? Are they allowed?