Is Yi's Legend Ability (which uses 'while' language) a trigger or a passive ability?

Ruling: Yi's Legend Ability is a passive ability, not a trigger. Abilities using "while" language are passive and the bonus is active whenever the condition is true.

Nuances:

• If there are 2 units on Yi's side in a showdown and one gets killed/moved before the combat damage step, the +2 bonus will no longer apply since the condition is no longer met.