Does Teferi's Protection protect your commander from commander damage being tracked?

Teferi's Protection gives you and your permanents protection from everything and phases out your permanents until your next turn (CR 702.97). While phased out, your permanents cannot be targeted, damaged, or otherwise affected — and you personally have protection from everything, meaning you cannot be dealt damage either. So during the turn(s) Teferi's Protection is active, no new commander damage can be accumulated against you.

However, commander damage is a cumulative, persistent tally tracked throughout the entire game (CR 903.10a). The rules state that if a commander has dealt 21 or more combat damage to a player over the course of the game, that player loses. There is no mechanic that resets or erases this running total — not phasing, not protection, not life gain, nothing.

So Teferi's Protection does NOT wipe or reduce the commander damage already recorded. If an opponent's commander had dealt you 18 damage before you cast Teferi's Protection, you still have 18 recorded against you when the effect ends. Three more combat damage from that same commander on a later turn will still cause you to lose.

What Teferi's Protection does do is prevent any additional commander damage from being dealt during the turns it is active, effectively buying you time. It is a powerful defensive tool, but it is not a reset button for the damage tracker.

Example: Opponent's Atraxa has dealt you 19 combat damage over several turns. You cast Teferi's Protection on your turn. Atraxa cannot deal you damage while the effect lasts — but the moment it wears off, those 19 points are still on the books. Two more combat damage from Atraxa on a subsequent turn means you lose at 21.