Cannot display workflow state change form on unpublished content

Yep, this seems to be a feature. Need to find out the initial requirement, before this can be removed/replaced.
Apparently, you cannot see the value of the state, too.

You might want to patch the code, and remove the check on '$node->status' (or $entity->status in 7.x-2.x).

This would be desirable. We are hoping to use workflow like this:

1) Private content created by the end user (unpublished).
2) Approved by the user's line manager, without the possibility of editing ie approved by viewing the node.

Still need to find the reasoning behind this.
some previous discussions:
#786500: Do Workflow permissions override Drupal core permissions?
#438808: Without node permissions Author/Content Admin can't edit unpublished content
#156028: Workflow nodes must always be published for access controls to apply
Most discussions consider the usage of the workflow_access module.
Perhaps is is obsolete, with new permissions in D7:
- View (own) unpublished content
- Create content
- Edit own/any content

Haven't found the commit adding the $node->status check.
[EDIT] found this commit from March 10, 2013: #1380954-38: Triggers Missing
http://drupalcode.org/project/workflow.git/commitdiff/fcb543a3dfaf9b2bcd...

I consider creating a checkbox that enables/disables this check.

According to Nancy: "It may have had something to do with the Revisioning module. But I do not recall exactly."

Above commit removes this. Found no reason why this is introduced 1 year ago.