Messages

Tefari's emblem states "You may use a planeswalker's ability on any player's turn any time you could cast an instant." Isn't the wording of this card meant to fully override that current ruling of when you can use walker abilities? I mean, you can cast an instant in response to many things: upkeep, entering combat, declaring attackers, declaring blockers, not declaring blockers, end step, anytime a player does anything. I honestly don't think you're limited to just once per turn with this emblem. Since the card is overriding an existing ruling, I'd think if they wanted to keep that part of it, it would say "You may do this only once per turn." since we have precedence for that wording.

If that were true, you could activate a planeswalker's ability in response to activating its abilities.  That would result in activating any plansewalker an infinite amount of times per turn.  WotC would not give us a card that powerful, ever.  Now, I wouldn't mind this being true, but it turns Tefari into an instant win-con: drop tefari, ultimate him, activate every plansewalker you control until you kill the opponent using some combination of abilities.  WotC would never give us a card so oviously broken.

Well according to the rules you can only play a planeswalker ability once per turn so you wouldn't be activating it infinite times