You "just" need (yeah, easier said than done) to ensure that any intervention from an admin is publicly logged. If admin "foo" removes some content from user "bar", it should just be made visible, something like "user foo removed offensive content from user bar" or "that comment was edited by user foo". The problem here with reddit was not the fact that content was edited, it was that content was edited without anyone knowing it.
The tricky thing is that the admin team is still doing things that you want and need out of a reddit alternative. For example, ensuring that child pornography isn't getting shared. The question is how to set things up so that the right content gets removed while ensuring that how we decide what the right content to remove gets isolated from political pressures that want to influence the narrative.