You have multiple products in one ideas portal and you are using different workflows for at least one of them. Because the workflow is different, but you may have named a status the same in both, that status shows up twice.
If you have more than one product in a portal, then all of the workflows will show up. If they are all using the same workflow, you'll only have one set of statues showing. If you have more than one workflow, you'll have duplicates (if they are all named the same).
The solution is to either use the same idea workflow for all products or to rename statuses in each so that they are distinct.