How about making it more alarmingly obvious that you can edit your node? Simple stuff like changing the 'submit/stumbit' button to 'edit' or 'update' when you're viewing one of your own nodes? From what I can see there is nothing to suggest to the really clueless first time user what's actually going to happen if you edit your text beneath your post -- does it get resubmitted twice?
Excellent idea! I've started making the changes to allowing editting of root nodes and I'm also changing 'submit' to 'create' on preview pages and 'submit' to 'update' on edit pages.