Using the untap/tap ability of this planeswalker does not actually tap or untap. Loyalty counter still increases though.
Steps to reproduce:
Play Teferi, Who Slows The Sunset
Activate first ability and attempt to untap an artifact and/or a land and/or a creature
Observe that loyalty counter increases but spells are not tapped/untapped
Using the untap/tap ability of this planeswalker does not actually tap or untap. Loyalty counter still increases though.
Steps to reproduce:
Play Teferi, Who Slows The Sunset
Activate first ability and attempt to untap an artifact and/or a land and/or a creature
Observe that loyalty counter increases but spells are not tapped/untapped
Platform: PC