In multiplayer showdowns, can non-combatting players play actions/reactions, and do they need to be 'invited' by the attacker or defender?

Ruling: The "invited" rule has been removed from the current rules. Priority passes clockwise during showdowns, allowing all players to participate without needing an invitation.

Nuances:

• The Tabletop Simulator rulebook contains outdated rules that still reference the invitation system
• The official core rules no longer include the invitation mechanic