Re: destructive hdd check
The trouble with repeated confirmations ("Are you sure?", "Are you really sure?", "Have you actually thought this through?" and so on) is that they don't actually induce careful consideration. It tends to be more a case of Y-Y-Y-Y-ohshit".
A better approach is something like "Please type 'I REALLY WANT TO FORMAT DRIVE A:' to continue", with appropriate mechanisms to disable command recall and copy/paste. Even better would be something that changes every time it's used, but that would be tricky to implement on CP/M.