So many questions! But I’m here for it haha.
Delete is in NIP-09, edit is in NIP-23, expiring message are in NIP-40. The problems are solved technically, just not implemented in many clients.
I don’t know of any reputation systems that are really good! I haven’t done much research there.
Customers always own their relationship with business owners, because they can stop paying at any time. What I had in mind here are content-creators who get locked into a platform’s walled garden: Twitch, YouTube, Patreon, etc. They can’t leave and take their customers to a different app.
Maybe it is better to have multiple apps! Idk.