Key derogatories are a relatively new status update and primarily used by EX from what I''ve read - they are now using KD to represent any major derog. and it apparently destroys your score - im not sure about activity after a DV - I know they are not allowed to continue collection activites but I'm not sure if that also means they cannot contiue to report "accurately" - I'd be interested to know this too
THey are not allowed to post any negative information pending a debt validation. Various courts have ruled that posting kds are a form collection activity. Which makes sense, why else would they be harming your credit score if not to get you to feel cooerced enough to give them what they want. Try reading fdcpa section 809.