We're using the dropbox format with hierarchical select to let our customers choose flavors for a tin of popcorn. The flavors are all taxonomy terms and are grouped.

We'd really like to allow the same term to be selected multiple times. So, we allow up to 3 selections. But, if the person wants two of the same flavor, we want to allow that.

As it is now, they can't add the same term a second or third time if it's already been selected once.