1. Create any character you want, so long as you give it the Stoic pose.
2. Use the console to give yourself a scroll of Firebrand (or, you know, roll a Druid and pick Firebrand as one of your spells.)
3. Enter combat and cast Firebrand.
4. Check your inventory screen.
Observe that your character is positively committing harakiri with Firebrand, like this:
I imagine the issue stems from summoned weapons' not triggering the "weapon in hand" stance.