Watching him use ED on the teletype, the lack of ED's interactivity and terseness suddenly makes sense! Though obvious now, it never occurred to me that the tool was designed around physical printing interfaces.
All of UNIX was. Right down to the decision for commands like cp (not copy!) to not print anything unless there's an error. A decade later MS-DOS could be profligate and waste virtual ink printing friendly messages like "2 file(s) copied."
