Do we need self moderation of topics?why not feature two views of the topics? 1. normal view 2. edited view.
In normal view everything as usual while edited view displays a public record that says: "A" was changed to "B" on the date "C" . Message entries removed by author marked with a link leading to the removed post contents. Thus deniability is avoided.
People go with default settings so they will only change view for controversial topics.