Why does Tactical Advisors have the text "Once per battle"? I thought that all actions (unless otherwise stated) were once per turn? Does this mean that if I have 2 Tactical Advisors in play, that I can only use the ability on one of them?
Tactical Advisors - Once per battle
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Why does Tactical Advisors have the text "Once per battle"?
In order to override the "once per turn" default restriction that affects all abilities.
I thought that all actions (unless otherwise stated) were once per turn?
This is true for all abilities by default, unless their text says otherwise, as this Follower's text does (see below, emphasis mine). Abilities and actions: "abilities can be used only once per turn, unless a different usage limit is stated (Example: “Twice per turn” or “once per game.”)"
Does this mean that if I have 2 Tactical Advisors in play, that I can only use the ability on one of them?
No, this means that if you take the Battle action on one of your Tactical Advisors during a battle, and later this turn its unit is at the current battlefield during another battle, you can legally use its ability again, as long as you do not use it more than once per battle.
Different copies of Tactical Advisors are used independently. If you take the action on one of them, it does not prevent you from using the ability on other copies. Special wording rules, References: "References to the card’s title, or to a shortened form of the title in the case of Personalities (such as “Kei” as short for “Mirumoto Kei”), refer to the card itself. Such references by title refer only to that copy of the card, not to any other copy that might exist, unless they use wording such as “a Mirumoto Kei” or “a copy of Mirumoto Kei.”"