Re: Recursive edits in `save-excursion'

[Richard Stallman]

The explanation for this is that save-excursion saves the current
buffer, but what you set when you switch buffers is the selected
window's buffer.  save-excursion does not restore that.  The first
save-excursion restores the original current buffer but doesn't
switch to it.  The second recursive edit notices that the current
buffer isn't the same one you've switched to, so it arranges to
save and restore the current buffer.

I will document this.