Wait, someone stores their bank account info at MD? What did they do? Send their bank account via message or something? Also correct me if I'm wrong, the thing you need to worry about is your username+password combination, right? Like you can delete your MD account, but if you use the same combination 69 times in other sites, deleting your account doesn't solve anything if the password is already leaked?
Edit: My account info was leaked during that Adobe situation years ago and this was explained to me that way, so yeah.