Krovikan Plague,
Nature's Chosen, &
Veteran's Voice
These three Auras from Alliances all said "tap enchanted creature to" do something. We've interpreted this as the cost of an activated ability. However, somewhere along the way these became abilities granted to the enchanted creature. This is relevant for you Muraganda Petroglyphs fans out there but in the case of Nature's Chosen, the differences are even more dramatic: the once-a-turn restriction didn't follow the ability if the Aura gets moved to a new creature. We can put that back and make Krovikan Plague's last ability a bit easier to parse.
New Krovikan Plague wording
Citation :
Enchant non-Wall creature you control
When Krovikan Plague enters the battlefield, draw a card at the beginning of the next turn's upkeep.
Tap enchanted creature: Krovikan Plague deals 1 damage to target creature or player. Put a -0/-1 counter on enchanted creature. Activate this ability only if enchanted creature is untapped.
New Nature's Chosen wording
Citation :
Enchant creature you control
: Untap enchanted creature. Activate this ability only during your turn and only once each turn.
Tap enchanted creature: Untap target artifact, creature, or land. Activate this ability only if enchanted creature is white and is untapped and only once each turn.
New Veteran's Voice wording
Citation :
Enchant creature you control
Tap enchanted creature: Target creature other than the creature tapped this way gets +2/+1 until end of turn. Activate this ability only if enchanted creature is untapped.