The AI ITS machines I think weren't used by non-technical users much, the TOPS-20 machines might be, but the anecdote I heard was always in context of Multics, which had much more explicit time sharing story behind it (with computing as utility).
I don’t know why you say that — the ITS machines were used by everybody in 545 tech square, researchers, admins and “secretaries” alike (both AI and LCS), from when I was there until they were gradually retired. The one TOPS-20 machine, Oz, didn’t arrive until times had changed and a lot of alternatives were already in use.
As for time sharing: ITS stands for “Incompatible Timesharing System” (a joke on CTSS), with memory protection, etc used by multiple users on terminals and over the net starting around/before the Multics project (all of which preceded Emacs of course)
Multics was also at 545 tech square, from 1967 to 1988.
ITS version 1 is counted from 1967 as well (first mentions of PDP-6 ITS), simply because Project MAC couldn't deliver computing resources needed by other groups, not to mention AI Lab tended to modify the hw all the time (a fate AFAIK common to all ITS systems).
The anecdote about secretaries extending Emacs came from RMS, describing a group that used the shared "utility" computing resources provided by Project MAC (later turned into LCS) and who used a manual that didn't mention the word programming, compiled by who-knows-who, which showed how to modify Multics Emacs (which was the second Lisp-based Emacs) to user's liking.
But its very possible -- I never interacted with any non-programmer Multics users.