The elements in dropdowns for non-tagging taxonomies should have CSS classes.
For example, parent-child relationships are currently only indicated by position in the list and a dash before the child element. I would like to add my own CSS so that I modify the appearance of parent elements to make parents more obvious.
I think this should be a core enhancement. It would bring the dropdown up to the standard of other parts of Drupal, where rich CSS class use allows great styling flexibility.
Note that I realize new features probably belong in the 7.x queue. However, I am not sure what 7.x supports and am trying to discern at #647958: Non-tagging taxonomy features are gone.
I reviewed the other taxonomy modules (http://drupal.org/node/212834), and neither of the 6.x ones do this.