Yo! Glad to see the game getting more attention (and looking forwards to the errata pass!).
Our group had a couple of assorted rule questions and comments after play- we made spot calls as needed, but we wanted to raise them as concerns/questions for errata;
1. Question about whether 0 damage counts as damage (answered below).
2. Can you spend any number of iron tokens on one hit (suggested by Armored Style, page 69), or just 1-2 (Glossary, page 280)?
3. How does 'priority' work? If someone wants to take an action during someone else's turn (ex. a token action), can they take as many token actions as they like before that person can take a Simple Action or use Free Movement? Can the person who's turn it is interrupt with their own token action? We generally settled on 'one side has a chance to take an action, then the other side has a chance to take an action'.
4. If a Copy moves into a space with an obstacle (particularly a Trap) using movement, what happens? Do they just coexist?
5. How do actions with an X in their cost interact with cost reduction (Elder, Phantom)? Can we treat them as a 'tiered action' with effectively infinite tiers (one for each possible die roll? Edit: Looked at Waiting Game- I'm going to guess they aren't affected by cost reduction, lol
6. This is a really goofy edge case, but a player actually did this- if someone takes Forbidden Power/Iron can they just not move? Is it split 50%/25%/25%? Our GM ruled that every 2 Speed Tokens effectively generated 1 Power and 1 Iron and 1 Speed (they were quite strong in combat, but it felt pretty fair overall- we had a strong party)
7. Play feedback- Necromancer making copies anywhere in line of sight felt like it could have very easily been overwhelming in combination with a mobile foe due to giving it effectively infinite range- the damage was low impact compared to the ability of the Boss to summon a copy at the start of their turn and then menace us at long range 'for free'. This might be working as intended, but it doesn't feel like the horde playstyle suggested by Necromancer.
8. When a character has a Copy take an action, my understanding is that this means 'you are taking the action, but from the position of the Copy', e.g. the player could, for example, spend Power tokens on behalf of the Copy, or discard their Challenge token if the Copy's action dealt damage to your Challenge target- is this correct?
9. Can you hit a single Mook foe multiple times with stuff like a 3+ Shockwave or Whirlwind if they have multiple bodes in range?
10. Play feedback- Challenge tokens are crazy impactful, and can virtually shut down Song Warriors, which may be completely unable to break through defensive walls or even get in range quickly. Fun, but felt on the edge of being an OP mechanic, with certain builds and situations making it nearly impossible to take any action- when everyone's challenged by one Bring It On!, nobody can even Put It Out! to clear a challenge.