I try to look before submitting, ninja edit if fast enough if I catch it, but if not, or if I need to correct myself because of later replies showing I'm an idiot, I'll do an EDIT: at the bottom, and depending on context, also reply to the person that I changed it due to the discussion. That's the part that annoys me and not much can be done about it - all the people who read your mistake but never replies or came back to see the edit. The last thing we need is some push notification that "UserX has edited their message that you read three days ago". Let it be.