Does this mean that units’ Might can go to 0 or below now?

Units’ Might could always go to 0 or below; it was just really hard to actually make it happen. For example: If a Recruit was at Trifarian War Camp, it would have 2 Might (its 1 base Might, +1 from War Camp). If it got hit with Stupefy, Stupefy would “snapshot” at -1 Might, reducing the Recruit’s Might to 1. If the Recruit then moved away from Trifarian War Camp, it would lose the +1 Might bonus and end up at 0 Might. It’s much easier to make it happen with Spiritforged cards, though, so it’s worth reviewing the rules for units with 0 or less Might.