However, setting goal-column disables line-move-visual, so <up> and
<down> only move by logical lines through the multiline elements.  I
also tried let-binding goal-column instead of setting it, but that had
no effect, i.e., same as the second patch above.

One difference between navigating through file-name-history or
buffer-name-history and navigating through extended-command-history is
that with the former, points is always at the end of the history element
(with my proposed change, otherwise at least at the end of a visual
line), while with the latter, point starts out at the beginning of the
history element.  The goal-column problem seems likely to be related to
this difference, but I currently don't have a solution for it.  So until
someone comes up with one, it may be best to stick with the status quo.

Steve Berman