I'm also concerned about people emptying root posts; if there's a way to allow minor edits without wholescale editing violence, I don't mind this idea.

I doubt it'll have much effect on duplicate posts, though. If someone is unable to comprehend the purpose of the "preview" button as well as the "If something looked unlike you expected it to you might need to check out Writeup Formatting Tips." message, I doubt an "edit post" link will fare any better.