I suspect Bob is exercising creative license in his description. To my knowledge, there isn't a formal playback functionality. This is because not everything in Emacs is strictly reversible.
Here are a few ways to achieve playback-like behavior:
You ought to be able to achieve the same result, at least in spirit, with the default
undo command (typically bound to
C-/ until there is nothing left to undo. Then, press
C-f. Now press
C-/ repeatedly to redo.
The undo/redo will appear "chunky". This is because
undo tracks "inserts" and not individual commands. For a detailed explanation of how
undo works, see the Reddit post "How Emacs Undo Works".
You can achieve a fine-grain undo with
undo-tree. User lawlist1 provides code that modifies the default to provide key-for-key undo:
(when (timerp undo-auto-current-boundary-timer)
(lambda () (add-to-list 'undo-auto--undoably-changed-buffers (current-buffer))))
(fset 'undo-auto-amalgamate 'ignore)
This will undo/redo character insertions, copy/paste, etc. You can navigate these easily with
undo-tree doesn't record movements. It only tracks changes.
The section quoted looks a lot like what displays in
C-h l runs
view-lossage which shows the last 300 commands. Keystrokes can also be logged in raw form to a "dribble" file using
(open-dribble-file FILE). I'm not aware of a way to "play back" lossage or a dribble, however.
Seeing which commands are most frequently used, the point Bob is emphasizing with his anecdote, can be achieved with keyfreq. Bin Chen's "How to be extremely efficient in Emacs" demonstrates its usage.
1If you like lawlist's snippet, give the post an upvote!