All experience counters are identical, no matter how you got them. For example, Katara's last ability will count experience counters that you got from the first ability, from another ability, from another copy of Katara, Waterbending Master, and so on.
2025-10-02 • wotc
The experience counter goes on you, the player, not on Katara. You will keep that counter even if Katara, Waterbending Master dies.
2025-10-02 • wotc