How to improve the clarity of hierarchical taxonomy terms in edit forms? I have a hierarchical taxonomy vocab. When I go to -say- a node edit form that uses this, with checkboxes, the hierarchy is represented simply by prepending a - for every level of depth. This really does not represent the hierarchy very well - it's hard to see, and ideally it would be semantic (nested list), or at least add a class on the container elements like taxonomy-level-N.

Is there a module for this? Or some other hack?
One way you could approach this is to use select boxes with an 'add more items' button.

I use Simple Hierarchical Select for single value selections in a taxonomy with levels, but there's no reason you can't use it for multiple selections.

If that module doesn't make an 'add more items' button pop up then put the field in a Field Collection, yes even by itself.  I know for a fact that you can have multiples of those.