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I'm not sure if the following feature exists (I haven't noticed though) but would be really good to have a notification icon on a post which has been edited after the last reply. Sometimes I get the feeling that I'm answering to a completely different question because the previous post has been edited after my reply. Also I've seen many posts like: "it's good to see how 'name' is playing with edit button", "have you edited the post?", "why did you delete the post?" etc.