Two suggestions

[HQM@OZ <Henry Minsky at MIT-OZ>]

In ZWEI in Release 5.0 [GC'd Beta Test rev 3], FEP 17, Dusty plum, on Lisp Machine John Lennon (3600):

  Has anyone thought of implementing the hyper-UNDO command that RMS has
in MIT LISPM systems? I find it much more useful than the restricted UNDO
command currently in use.

Also, this is not ZWEI related, but I think the ABORT-TRIVIAL-ERRORS feature in MIT sytems is good,
because it bothers me to wait 3 seconds when I mistype an open paren and have the error system
swap in.