Under what circumstances are we supposed to add "Edited" in our posts?

I don’t think it’s any kinda rule or guideline that you have to add it when editing something. I guess you add it whenever you want people to know that your post has been edited.

There is no rule. It’s more of a courtesy than anything else. It lets people know the post might be different from when they first read it. So like @Symbeline said, use it when you want people to know that your post has been edited.

There is no rule about this. if you edit a post within 10 minutes there is no need to say it has been edit. I, and other people, may say “Edit” before a later post that corrects something in the former post that was noticed after the 10 minute period.

I agree with @SavoirFaire. It’s just to flag people that what they just saw, and responded to, has changed.

Wow, I really didn’t think anyone cared that much.

We care, @rojo. We care. sniffs dramatically