I don’t have an answer, except for "accept as little data as possible, avoid having centralized control". Basically decentralize all the things, especially control. It is unlikely that empty words will help you if taking down your site could stop something illegal from happening.
Due to this I disabled comments on all my websites, because I no longer had the time to moderate them. My GNU social instance only shows others the content I explicitly like or re-share — that’s active moderation with a white-list.
If unsure, don’t run the service. Just provide the tools others could use to run it and allow the others to accept money to fund their due dilligence.
I’m working on Freenet, and the kind of change I would reject off-hand is one which would give me more power. If some sort of control is needed, find a way to implement it without getting power yourself.
Besides: From your title I expected to see a question about copyleft — there the answer is: Use the AGPL which requires people who use your code to provide the code to all their users.
