Re: The *Warnings* buffer and undo

[Richard Stallman]

    Unrecorded changes turn the existing undo history useless.  While it
    could conceivably be nice if user changes could be undone, this won't
    work out.  The best that a program could do in this regard is set
    buffer-undo-list to t before doing its changes, and to nil afterwards.

That sounds like a good solution -- better than suppressing undo 100%
in that buffer.